A274511 a(n) is the only number m such that 7^(2^m) + 1 is divisible by A273948(n).

1, 3, 7, 4, 7, 2, 10, 9, 6, 15, 11, 14, 3, 5, 11, 12, 8, 17, 19, 5, 7, 21, 21, 4, 34, 25, 5, 9, 6, 20, 32, 17, 31, 40

Offset

1,2

Links

Table of n, a(n) for n=1..34.

Mathematica

t = Select[Prime@ Range[3, 10^7], IntegerQ@ Log2@ MultiplicativeOrder[7, #] &]; Table[SelectFirst[Range@ 100, Divisible[7^(2^#) + 1, t[[n]]] &], {n, Length@ t}] (* Michael De Vlieger, Jun 29 2016, after Arkadiusz Wesolowski at A273948 *)

Prog

(PARI) forstep(p=3, 10^15, 2, if(!Mod(p, 7)==0, if(isprime(p), o=znorder(Mod(7, p)); x=ispower(2*o); if(2^(x-1)==o, print1(x-2, ", ")))));

Crossrefs

Cf. A273948.

Sequence in context: A305202 A340013 A192265 * A371332 A179706 A231325

Adjacent sequences: A274508 A274509 A274510 * A274512 A274513 A274514

Keyword

nonn,more

Author

Arkadiusz Wesolowski, Jun 25 2016

Status

approved