A344897 - OEIS

%I #23 May 13 2022 12:27:58

%S 2,2,2,8,4,4,4,4,4,32,8,24,8,8,16,128,32,16,8,4,16,192,16,32,8,32,8,

%T 128,16,8,128,4,16,384,16,32,64,16,8,768,16,8,128,16,16,4096,16,16,

%U 512,16,128,256,16,4,64,768,32,64,32,16,64,8,8,3072,8,64,256,4,16,1024,2048,8,32,16,128,2048,64,3072,128,16

%N a(n) is the number of divisors of 10^n + 1.

%C a(n) is even because 10^n + 1 is not a square number.

%H Max Alekseyev, <a href="/A344897/b344897.txt">Table of n, a(n) for n = 0..331</a>

%F a(n) = A000005(A000533(n)).

%t a[0] = 2; a[n_] := DivisorSigma[0, 10^n + 1]; Array[a, 60, 0] (* _Amiram Eldar_, Jun 01 2021 *)

%o (PARI) a(n) = numdiv(10^n+1);

%Y Cf. A000005, A000533, A003021, A038371, A046798, A057934, A070528, A119704, A344859, A087021, A087022,

%K nonn

%O 0,1

%A _Seiichi Manyama_, Jun 01 2021