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A081762 Primes p such that p*(p-2) divides 2^(p-1)-1. 6
3, 5, 17, 37, 257, 457, 1297, 2557, 4357, 6481, 8009, 11953, 26321, 44101, 47521, 47881, 49681, 57241, 65537, 74449, 84421, 97813, 141157, 157081, 165601, 225457, 278497, 310591, 333433, 365941, 403901, 419711, 476737, 557041, 560737, 576721, 1011961, 1033057 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes p such that p-2 divides 2^(p-1) - 1.  The only member in A006512 is 5. - Robert Israel, Dec 03 2014

N=647089 is the smallest composite number such that (n-1)^2-1 divides 2^(n-1)-1. - M. F. Hasler, Jul 24 2015

LINKS

Robert G. Wilson v, Table of n, a(n) for n = 1..1076 (first 303 terms from Chai Wah Wu)

MAPLE

select(p -> isprime(p) and 2 &^ (p-1) - 1  mod (p-2) = 0, [seq(2*i+1, i=1..10^6)]);  # Robert Israel, Dec 03 2014

PROG

(PARI) lista(nn) = {forprime(p = 3, nn, if (! ((2^(p-1)-1) % (p*(p-2))), print1(p, ", ")); )} \\ Michel Marcus, Dec 02 2013

(Python)

from sympy import prime

from gmpy2 import powmod

A081762_list = [p for p in (prime(n) for n in range(2, 10**5)) if powmod(2, p-1, p*(p-2)) == 1] # Chai Wah Wu, Dec 03 2014

CROSSREFS

Sequence in context: A019414 A249131 A260406 * A148515 A148516 A148517

Adjacent sequences:  A081759 A081760 A081761 * A081763 A081764 A081765

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Apr 09 2003

EXTENSIONS

More terms from Michel Marcus, Dec 02 2013

STATUS

approved

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Last modified October 22 19:53 EDT 2019. Contains 328319 sequences. (Running on oeis4.)