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A303994 Numbers whose sum of divisors is the fourth power of one of their divisors. 7
1, 510, 642, 3394440, 3629640, 3653640, 3663240, 3673080, 3701160, 3736920, 3901080, 3958680, 4077960, 4137240, 4240920, 4251480, 4256520, 4273320, 4274520, 4319880, 7300854, 12798240, 13362720, 14405664, 15170820, 16173024, 16342368, 16354884, 16361184, 16957668, 17113404 (list; graph; refs; listen; history; text; internal format)
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
Sequence in context: A071687 A345361 A048254 * A249551 A248790 A252877
KEYWORD
nonn
AUTHOR
Paolo P. Lava, May 04 2018
EXTENSIONS
More terms from Michel Marcus, May 05 2018
STATUS
approved

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Last modified March 2 07:45 EST 2024. Contains 370460 sequences. (Running on oeis4.)