OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..5000 (terms 1..100 from Paolo P. Lava)
EXAMPLE
Divisors of 189 are 1, 3, 7, 9, 21, 27, 63, 189, sigma(1) = 1, sigma(3) = 4, sigma(7) = 8, sigma(9) = 13, sigma(21) = 32, sigma(27) = 40, sigma(63) = 104, sigma(189) = 320. (1^3 + 4^3 + 8^3 + 13^3 + 32^3 + 40^3 + 104^3 + 320^3) / 189 = 179854.
MAPLE
with(numtheory); ListA226565:=proc(q) local a, b, k, n;
for n from 1 to q do a:=[op(divisors(n))]; b:=add(sigma(a[k])^3/n, k=1..nops(a));
if type(b, integer) then print(n); fi; od; end: ListA226565 (10^6);
MATHEMATICA
Select[Range[4000], Divisible[Total[DivisorSigma[1, #]^3&/@Divisors[#]], #]&] (* Harvey P. Dale, Sep 17 2019 *)
s[n_] := DivisorSum[n, DivisorSigma[1, #]^3 &]; Select[Range[3600], Divisible[s[#], #] &] (* Amiram Eldar, Jul 01 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Jun 11 2013
STATUS
approved