A387157 a(n) = A173557(sigma(n)), where A173557(n) is multiplicative with a(p^e) = p-1 and sigma is the sum of divisors function.

1, 2, 1, 6, 2, 2, 1, 8, 12, 2, 2, 6, 6, 2, 2, 30, 2, 24, 4, 12, 1, 2, 2, 8, 30, 12, 4, 6, 8, 2, 1, 12, 2, 2, 2, 72, 18, 8, 6, 8, 12, 2, 10, 12, 24, 2, 2, 30, 36, 60, 2, 6, 2, 8, 2, 8, 4, 8, 8, 12, 30, 2, 12, 126, 12, 2, 16, 12, 2, 2, 2, 96, 36, 36, 30, 24, 2, 12, 4, 60, 10, 12, 12, 6, 2, 20, 8, 8, 8, 24, 6, 12, 1, 2, 8

Offset

1,2

Links

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

Formula

a(n) = A003958(A080398(n)).

Mathematica

A387157[n_] := If[n == 1, 1, Times @@ (FactorInteger[DivisorSigma[1, n]][[All, 1]] - 1)];
Array[A387157, 100] (* Paolo Xausa, Aug 20 2025 *)

Prog

(PARI) A387157(n) = factorback(apply(p -> p-1, factor(sigma(n))[, 1]));

Crossrefs

Cf. A000203, A003958, A080398, A173557, A387158 (positions where equal to A173557(n)).

Cf. also A351442.

Sequence in context: A321352 A134134 A222005 * A351442 A325815 A292441

Adjacent sequences: A387154 A387155 A387156 * A387158 A387159 A387160

Keyword

nonn

Author

Antti Karttunen, Aug 19 2025

Status

approved