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A303993 Numbers whose sum of divisors is the cube of one of their divisors. 6
1, 102, 8148, 63720, 66120, 71880, 196896, 446040, 452760, 462840, 471960, 503160, 517320, 544920, 549240, 554280, 559320, 575880, 756400, 1458912, 1499232, 1579872, 1634040, 1659960, 1748520, 5294800, 9740640, 10103520, 11103456, 11438280, 11583264, 11619720, 11915640 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Subset of A020477.
LINKS
EXAMPLE
Divisors of 102 are 1, 2, 3, 6, 17, 34, 51, 102 and their sum is 216 = 6^3.
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]^3 then print(n); break; fi; od; od; end: P(10^9);
MATHEMATICA
Select[Range[10^6], Mod[#, DivisorSigma[1, #]^(1/3)] == 0 &] (* Michael De Vlieger, May 06 2018 *)
PROG
(PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 3) && !(n % sqrtnint(s, 3))); \\ Michel Marcus, May 05 2018
CROSSREFS
Sequence in context: A217331 A284448 A274252 * A030512 A097725 A353142
KEYWORD
nonn,easy
AUTHOR
Paolo P. Lava, May 04 2018
STATUS
approved

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Last modified June 22 14:17 EDT 2024. Contains 373587 sequences. (Running on oeis4.)