cp's OEIS Frontend

A303994 Numbers whose sum of divisors is the fourth power of one of their divisors.

%I A303994 #26 Nov 05 2023 15:19:16
%S A303994 1,510,642,3394440,3629640,3653640,3663240,3673080,3701160,3736920,
%T A303994 3901080,3958680,4077960,4137240,4240920,4251480,4256520,4273320,
%U A303994 4274520,4319880,7300854,12798240,13362720,14405664,15170820,16173024,16342368,16354884,16361184,16957668,17113404
%N A303994 Numbers whose sum of divisors is the fourth power of one of their divisors.
%C A303994 Subset of A019422.
%H A303994 Giovanni Resta, <a href="/A303994/b303994.txt">Table of n, a(n) for n = 1..1565</a> (terms < 10^12; first 398 terms from Robert Israel)
%e A303994 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.
%p A303994 with(numtheory): P:=proc(q) local a,k,n;
%p A303994 for n from 1 to q do a:=sort([op(divisors(n))]);
%p A303994 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);
%t A303994 Select[Range[17114000],MemberQ[Divisors[#]^4,DivisorSigma[1,#]]&] (* _Harvey P. Dale_, Jul 22 2021 *)
%o A303994 (PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 4) && !(n % sqrtnint(s, 4))); \\ _Michel Marcus_, May 05 2018
%Y A303994 Cf. A000203, A019422, A303123, A303993, A303995, A303996.
%K A303994 nonn
%O A303994 1,2
%A A303994 _Paolo P. Lava_, May 04 2018
%E A303994 More terms from _Michel Marcus_, May 05 2018