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A226566

Numbers k such that Sum_{d|k} sigma(d)^3/d is an integer, where d are the divisors of k.

1, 201, 981, 1962, 3663, 7326, 10791, 12753, 15879, 21582, 25506, 30411, 56898, 60822, 135749, 140283, 172161, 212454, 266727, 280566, 334521, 344322, 360027, 395343, 399267, 407247, 507177, 625878, 669042, 720054, 739674, 790686, 798534, 881919, 1014354, 1221741

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OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..510 (terms below 10^10)

EXAMPLE

Divisors of 981 are 1, 3, 9, 109, 327, 981.

sigma(1) = 1, sigma(3) = 4, sigma(9) = 13, sigma(109) = 110, sigma(327) = 440, sigma(981) = 1430.

(1^3/1 + 4^3/3 + 13^3/9 + 110^3/109 + 440^3/327 + 1430^3/981) = 3253822.

MAPLE

with(numtheory); ListA226566:=proc(q) local a, b, k, n;

for n from 1 to q do a:=[op(divisors(n))]; b:=add(sigma(a[k])^3/a[k], k=1..nops(a));