A291360 Prime divisors of 2^720 - 1.

3, 5, 7, 11, 13, 17, 19, 31, 37, 41, 61, 73, 97, 109, 151, 181, 241, 257, 331, 433, 577, 631, 673, 1321, 23311, 38737, 54001, 61681, 8369281, 18837001, 29247661, 394783681, 4278255361, 4562284561, 46908728641, 168692292721, 487824887233, 469775495062434961, 750016890283777055704738227247474485366338380663681

Offset: 1

Author

Arkadiusz Wesolowski, Aug 23 2017

Keywords

• nonn
• easy
• fini
• full

Comments

It is possible to find an odd positive integer k and a set S = {p(1), ..., p(s)} containing only primes which appeared in the sequence such that for any nonnegative integer n, k*2^n + 1 == 0 (mod p(i)) and k*2^n - 1 == 0 (mod p(j)) for some p(i) and some p(j) from the set S.

Links

• Index entries for sequences related to divisors of numbers

Crossrefs

Cf. A076335, A154700. Supersequence of A269326.

Programs

Magma

PrimeDivisors(2^720-1);

Mathematica

Select[Divisors[2^720-1], PrimeQ]

PARI

forprime(p=1, , if(Mod(2, p)^720==1, print1(p, ", "))) \\ Felix Fröhlich, Aug 23 2017