A178970 - OEIS

%I #21 Jun 27 2024 22:18:04

%S 2,3,4,2,6,7,2,9,10,2,12,8,20,15,16,2,22,19,2,21,22,38,24,32,2,27,52,

%T 2,30,31,2,8,34,2,36,37,17,43,40,20,42,8,2,45,32,2,27,49,29,51,52,23,

%U 54,55,2,57,77,11,15,28,2,108,64,2,66,32,47,69,70,2

%N a(n) = 2^(2n-1) mod (2n+1).

%F a(n) = A081294(n) mod A005408(n).

%e a(1) = 2^(2*1-1) mod (2*1+1) = 2^1 mod 3 = 2.

%t f[n_] := PowerMod[2, 2 n - 1, 2 n + 1]; Array[f, 70] (* _Robert G. Wilson v_, Jan 03 2011 *)

%Y Cf. A000079.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 03 2011