A387156 a(n) = A003557(sigma(n)), where A003557(n) is multiplicative with a(p^e) = p^(e-1), and sigma is the sum of divisors function.

1, 1, 2, 1, 1, 2, 4, 1, 1, 3, 2, 2, 1, 4, 4, 1, 3, 1, 2, 1, 16, 6, 4, 2, 1, 1, 4, 4, 1, 12, 16, 3, 8, 9, 8, 1, 1, 2, 4, 3, 1, 16, 2, 2, 1, 12, 8, 2, 1, 1, 12, 7, 9, 4, 12, 4, 8, 3, 2, 4, 1, 16, 4, 1, 2, 24, 2, 3, 16, 24, 12, 1, 1, 1, 2, 2, 16, 4, 8, 1, 11, 3, 2, 16, 18, 2, 4, 6, 3, 3, 8, 4, 64, 24, 4, 6, 7, 3, 2

Offset

1,3

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Formula

a(n) = A000203(n) / A080398(n).

a(n) = A062401(n) / A387157(n).

Mathematica

A387156[n_] := # / Times @@ FactorInteger[#][[All, 1]] & [DivisorSigma[1, n]];
Array[A387156, 100] (* Paolo Xausa, Aug 20 2025 *)

Prog

(PARI) A387156(n) = { my(s=sigma(n)); s/factorback(factor(s)[, 1]); };

Crossrefs

Cf. A000203, A003557, A062401, A080398, A387157.

Cf. also A386424, A386425.

Sequence in context: A136788 A334622 A136450 * A355011 A131054 A267998

Adjacent sequences: A387153 A387154 A387155 * A387157 A387158 A387159

Keyword

nonn

Author

Antti Karttunen, Aug 19 2025

Status

approved