## scanning – How do I keep my paper perfectly flat on flatbed scanner?

I am scanning a photobook, I have unbinded the book and scanning the pages one by one to my Epson Perfection v600. The problem I ran into is that the pages couldn’t lay completely flat on the bed, the pressure from the cover was not strong enough. It was okay for individual pages as they are not that noticeable but it became a problem when I have pages that needs to be stitch together in Photoshop, I have a hard time aligning them.

I tried putting credit card size cards on top of the paper but they were just way too small to cover the entire page. What other methods can I do?

## Gimp insists on changing Epson SC-P800 black to photo black on plain paper

I’m trying to print an image on plain paper with an Epson SC-P800 printer using GIMP 2.10 on MacOS 10.14.6 (Mojave). I can find no setting in the print or page-setup dialogs to set which black ink is used. When I attempt to print the printer is prompting me to switch to Photo Black.

## film – Can a LCD projector imprint an image onto a light-sensitive paper?

I am trying to develop an experiment in which I would expose a fast-framed video (almost timelapse-y) to a light-sensitive paper for a short amount of time as in the same process used to make photograms. However, I do not own an analog projector and I was wondering if it would work with a regular LCD projector. I have run a few experiments on a scanner, but unfortunately the light of projection and the light used by the scan to capture the image mostly cancelled itself out, due to the LCD nature of both, resulting in an overexposed image with a few dashes of what the projection was. Considering analog procedures don’t use that kind of light information, I thought it could work.

What do you think?

## bitcoin core – What needs to be written down for a paper wallet?

I’m installing `bitcoin-core` with `snap` on `Ubuntu` for a dry-run at generating a paper wallet.

Perhaps naively, I thought to “write down” something like:

``````nicholas@mordor:~/bitcoin\$
nicholas@mordor:~/bitcoin\$ ls
nicholas@mordor:~/bitcoin\$
nicholas@mordor:~/bitcoin\$ ssh-keygen -t ed25519 -C saunders.nicholas@gmail.com
Generating public/private ed25519 key pair.
Enter file in which to save the key (/home/nicholas/.ssh/id_ed25519): ./bitcoin_wallet
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in ./bitcoin_wallet
Your public key has been saved in ./bitcoin_wallet.pub
The key fingerprint is:
SHA256:MtZQUFLqDWU0fJbkFhner+ZRF1WZ1MacM0WOBbGPvCc saunders.nicholas@gmail.com
The key's randomart image is:
+--(ED25519 256)--+
|      o*O.++  +B&|
|       *.+=o   @*|
|      +  o+ . oo+|
|     . = .   o o.|
|      = S     = o|
|     . o     o o |
|            + E .|
|           o . o |
|            .    |
+----(SHA256)-----+
nicholas@mordor:~/bitcoin\$
nicholas@mordor:~/bitcoin\$ ls
bitcoin_wallet  bitcoin_wallet.pub
nicholas@mordor:~/bitcoin\$
nicholas@mordor:~/bitcoin\$ cat bitcoin_wallet
-----BEGIN OPENSSH PRIVATE KEY-----
b3...AAtzc2gtZW
QyNTUxOQAAACD...AAAKBLLY/ISy2P
yAAAAAt...jpB6ZXAZLiLoXx+D9kw
AA..JYB62mUlxCESA
KyOkHp...LmNvbQEC
-----END OPENSSH PRIVATE KEY-----
nicholas@mordor:~/bitcoin\$
nicholas@mordor:~/bitcoin\$ cat bitcoin_wallet.pub
ssh-ed25519 AAA..IuhfH4P2T saunders.nicholas@gmail.com
nicholas@mordor:~/bitcoin\$
``````

where I need the public and private key. Obviously, very easy to make a mistake, but isn’t that what’s required??

I’m not understanding all this mention of writing down seed words or passphrases. Isn’t the key pair required?

## signature – How can I sign a bitcoin address that is on a paper wallet?

I have a bitcoin address that shows I held the BTC prior to December 2019. I need to verify this but as the address refers to a paper wallet I don’t seem to be able to do so. If I move the coin to a hardware/software wallet I can verify BUT I will have created a new address that doesn’t meet the criteria in that case.

Is there a way to sign a message with my paper based bitcoin address? Or import the paper wallet into something that can sign messages?

## nt.number theory – Where can I find the paper by Lagarias?

Lagarias also proved, unconditionally, that

$$sigma(n) ; $$n>1$$

J. C. Lagarias, Problem 10949, A generous bound for divisor sums, American Math.
Monthly 109 (2002), 569. (Solution: 111 (2004), 264–265.)

Where can I find this paper? Or, any other links that shows how the inequality has been derived would be greatly appreciated.

EDIT: I will also accept the answer if anyone can outline the steps, how Lagarias derived his criterion.

## On Tarjan’s paper “Finding a Maximum Clique”

In his paper, “Finding a Maximum Clique” from 1972 Robert Tarjan introduced an algorithm that finds maximum cliques in $$O(1.286^n)$$. You can find a link to his paper here.

In the second page of the introduction he states the following lemma.

Let $$(V,G)$$ be a graph and $$S subseteq V.$$ Then
$$||G|| = max_{text{clique } C text{ in } G_S} {|C| + ||G_{A(C)setminus S}||}$$

where $$||G||$$ is the size of the maximum clique in $$G$$ and $$A(C)$$ is the set of adjacent vertices to one or more elements in $$C$$.

This does not make sense to me, for example if we let $$S$$ be the set containing just one isolated vertex, then $$max_{text{clique } C text{ in } G_S} {|C| + ||G_{A(C)setminus S}||} = 1$$, since $$A(C) setminus S = emptyset setminus S = emptyset$$.

Even worse, we can take $$S = emptyset$$ and then the lemma falls apart.

What am I missing?

## Can I send bitcoin from paper wallet directly to hardware wallet?

Paper wallets give you direct control of your funds and a single private key.

Some wallets have an import private key feature. Check if your Hardware wallet allows importing or sweeping.

What you want to do is sign a transaction for all of the unspent outputs that sends funds to one of the addresses on your Hardware wallet. This is often known as “sweeping”, when you take all available funds under an address and send them to a different address.

Most wallets will sweep funds to itself, as opposed to letting you enter any address to sweep to. Creating a sweep transaction on your own is an advanced technique for programmers and command-line junkies. You should be comfortable creating these types of transactions in a test environment before ever attempting to do so with real sums of money.

There are also tools and libraries available that will help you with this, just be very careful to only use a reputable source — there are many scams that want to steal your private key(s).

Recommendations on this site are strongly discouraged, so here are three (3) external examples that can help you sweep your funds.

• Samourai Wallet can sweep funds from private keys and QR codes.

• Electrum can sweep keys to any destination address. To sweep private keys, go to the Wallet menu -> Private Keys -> Sweep. Enter the private key in the appropriate field. By default the “Address” field is populated with an address from your existing electrum wallet. Change this to your one of your Hardware wallet addresses.

• Sweepkey is an open-source tool I created using the bitcoin-js library for my own usage that sweeps funds from a private key to any specified address (again not a recommendation just an example).

I cannot stress enough, be very careful when interacting with private keys in a hot(online) environment. It is best to never expose them to an online environment, but if you have to, please practice on testnet or with small amounts until you feel comfortable you know what you are doing.

## hecke algebras – Reference of Waldspurger’s paper : SUR LES COEFFICIENTS DE FOURIER DES FORMES MODULAIRES DE POIDS DEMI-ENTIER

I want to find reference of Waldspurger’s paper (SUR LES COEFFICIENTS DE FOURIER DES FORMES MODULAIRES DE POIDS DEMI-ENTIER)

the name of ref. is (W) J.L Waldspurger,Correspondance de Shimura
(J. Math. pures et appl., n 60, 1980, p.1-132)

Is there anyone who has the ref.?

and I don’t know the definition of Hecke algebra of
metaplectic group SL(2,A)*{1,-1}

There are many sence of Hecke algebra but I don’t know in the context of that paper.