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A303994 Numbers whose sum of divisors is the fourth power of one of their divisors. 6
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

Table of n, a(n) for n=1..31.

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);

PROG

(PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 4) && !(n % sqrtnint(s, 4))); \\ Michel Marcus, May 05 2018

CROSSREFS

Cf. A000203, A019422, A303123, A303993, A303995, A303996.

Sequence in context: A062914 A071687 A048254 * A249551 A248790 A252877

Adjacent sequences:  A303991 A303992 A303993 * A303995 A303996 A303997

KEYWORD

nonn,easy

AUTHOR

Paolo P. Lava, May 04 2018

EXTENSIONS

More terms from Michel Marcus, May 05 2018

STATUS

approved

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Last modified April 19 10:39 EDT 2019. Contains 322255 sequences. (Running on oeis4.)