A274512 a(n) is the only number m such that 10^(2^m) + 1 is divisible by A072982(n+1).

0, 3, 2, 1, 2, 7, 4, 4, 4, 4, 8, 7, 5, 15, 4, 7, 5, 9, 15, 3, 5, 8, 16, 19, 20, 17, 9, 12, 18, 6, 26, 8, 29, 8, 11, 19, 29, 35, 19, 40, 22, 41, 40, 5

Offset

1,2

Links

Table of n, a(n) for n=1..44.

Formula

a(n) = A197224(n+1) - 1. - Ray Chandler, Oct 25 2019

Prog

(PARI) forstep(p=3, 10^15, 2, if(!Mod(p, 5)==0, if(isprime(p), o=znorder(Mod(10, p)); x=ispower(2*o); if(2^(x-1)==o, print1(x-2, ", ")))));

Crossrefs

Cf. A072982, A197224.

Sequence in context: A127318 A362689 A349930 * A175947 A085068 A265027

Adjacent sequences: A274509 A274510 A274511 * A274513 A274514 A274515

Keyword

nonn,more

Author

Arkadiusz Wesolowski, Jun 25 2016

Status

approved