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A344897
a(n) is the number of divisors of 10^n + 1.
13
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
0,1
COMMENTS
a(n) is even because 10^n + 1 is not a square number.
LINKS
FORMULA
a(n) = A000005(A000533(n)).
MATHEMATICA
a[0] = 2; a[n_] := DivisorSigma[0, 10^n + 1]; Array[a, 60, 0] (* Amiram Eldar, Jun 01 2021 *)
PROG
(PARI) a(n) = numdiv(10^n+1);
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 01 2021
STATUS
approved