A344897 a(n) is the number of divisors of 10^n + 1.

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

Offset: 0

Author

Seiichi Manyama, Jun 01 2021

Keywords

• nonn

Comments

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

Links

• Max Alekseyev, Table of n, a(n) for n = 0..331

Crossrefs

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

Programs

Mathematica

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

PARI

a(n) = numdiv(10^n+1);

Formula

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