A092345 - OEIS

A092345

a(0)=1; a(n) = sigma_1(n) + sigma_3(n).

1, 2, 12, 32, 80, 132, 264, 352, 600, 770, 1152, 1344, 2072, 2212, 3120, 3552, 4712, 4932, 6852, 6880, 9240, 9664, 12024, 12192, 16440, 15782, 19824, 20480, 25168, 24420, 31824, 29824, 37512, 37344, 44280, 43392, 55352, 50692, 61800, 61600, 73800, 68964, 86784

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OFFSET

0,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: 1 + Sum_{k>=1} k*(k^2 + 1)*x^k/(1 - x^k). - Ilya Gutkovskiy, Mar 17 2017

MATHEMATICA

nxt[{n_, a_}]:={n+1, DivisorSigma[1, n+1]+DivisorSigma[3, n+1]}; NestList[nxt, {0, 1}, 50][[All, 2]] (* Harvey P. Dale, Apr 14 2021 *)

PROG

(PARI) a(n) = if(n == 0, 1, my(f = factor(n)); sigma(f, 1) + sigma(f, 3)); \\ Amiram Eldar, Jan 03 2025

CROSSREFS