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April 24

website that deals questions similar to french program

Is there a website that deals with questions like you are given a result and various numbers and you have to find ways to come up with the results? It is like Des Chiffres et des lettres, a French program.--Donmust90 (talk) 16:29, 24 April 2013 (UTC)Donmust90[reply]

It is Countdown (game show) in English. Try a search for 'countdown number solver', that should give a few. Dmcq (talk) 16:40, 24 April 2013 (UTC)[reply]

Prime factors of (G-1)/2

What is known about the prime factors of (G-1)/2 where G is Graham's number? Count Iblis (talk) 22:11, 24 April 2013 (UTC)[reply]

I'd say you'd need to calculate Graham's number before asking that question. And when the first term of the sequence has a power tower consisting of more 3s than the observable universe... Pokajanje|Talk 18:50, 26 April 2013 (UTC)[reply]

Modular arithmetic can often be used to find prime factors of numbers which are too large to calculate. For example, Googolplex + 10 has 57445 known prime factors at [1]. I don't know whether it's feasible to find some prime factors of Graham's number minus one which is a lot larger. PrimeHunter (talk) 00:08, 27 April 2013 (UTC)[reply]

According to OEIS:A152178, G-14 is divisible by 13. That means G-1 is also divisible by 13. For more, you could try asking User:Joule36e5 who posted to Talk:Graham's number/Archive 2#Interesting question. PrimeHunter (talk) 00:48, 27 April 2013 (UTC)[reply]