OFFSET
1,2
COMMENTS
Subset of A019422.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..1565 (terms < 10^12; first 398 terms from Robert Israel)
EXAMPLE
Divisors of 510 are 1, 2, 3, 5, 6, 10, 15, 17, 30, 34, 51, 85, 102, 170, 255, 510 and their sum is 1296 = 6^4.
MAPLE
with(numtheory): P:=proc(q) local a, k, n;
for n from 1 to q do a:=sort([op(divisors(n))]);
for k from 1 to nops(a) do if sigma(n)=a[k]^4 then print(n); break; fi; od; od; end: P(10^9);
MATHEMATICA
Select[Range[17114000], MemberQ[Divisors[#]^4, DivisorSigma[1, #]]&] (* Harvey P. Dale, Jul 22 2021 *)
PROG
(PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 4) && !(n % sqrtnint(s, 4))); \\ Michel Marcus, May 05 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, May 04 2018
EXTENSIONS
More terms from Michel Marcus, May 05 2018
STATUS
approved