A179003 - OEIS

%I #14 Jun 28 2024 03:25:38

%S 1,2,4,6,7,10,16,18,19,25,28,30,31,34,36,37,38,43,46,49,52,55,58,61,

%T 64,67,70,78,79,87,88,91,96,97,100,106,107,109,112,115,118,124,126,

%U 133,138,145,147,148,151,154,156,157,160,163,169,180

%N Numbers k such that 2^(2*k-1) mod (2*k+1) is prime.

%t fQ[n_] := PrimeQ@ PowerMod[2, 2 n - 1, 2 n + 1]; Select[ Range@ 180, fQ]

%Y Cf. A000040, A178537, A178970.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Jan 03 2011