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A274511 a(n) is the only number m such that 7^(2^m) + 1 is divisible by A273948(n). 0
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 (list; graph; refs; listen; history; text; internal format)
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: A198886 A305202 A192265 * A179706 A231325 A227108

Adjacent sequences:  A274508 A274509 A274510 * A274512 A274513 A274514

KEYWORD

nonn,more

AUTHOR

Arkadiusz Wesolowski, Jun 25 2016

STATUS

approved

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Last modified November 15 01:25 EST 2019. Contains 329143 sequences. (Running on oeis4.)