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A303995 Numbers whose sum of divisors is the fifth power of one of their divisors. 6
1, 3210, 3498, 3882, 6453804, 7873684, 7943640, 8028120, 8099880, 9112230, 9561990, 10079430, 182626920, 192651480, 196192920, 199939320, 200271960, 201632760, 203289240, 206367480, 206645880, 207815160, 208955160, 210368760, 210406680, 210717720, 211645560 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Subset of A019423.
LINKS
EXAMPLE
Divisors of 3210 are 1, 2, 3, 5, 6, 10, 15, 30, 107, 214, 321, 535, 642, 1070, 1605, 3210 and their sum is 7776 = 6^5.
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]^5 then print(n); break; fi; od; od; end: P(10^9);
MATHEMATICA
Select[Range[10^4], IntegerQ[t = DivisorSigma[1, #]^(1/5)] && Mod[#, t] == 0 &] (* Giovanni Resta, May 04 2018 *)
PROG
(PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 5) && !(n % sqrtnint(s, 5))); \\ Michel Marcus, May 05 2018
CROSSREFS
Sequence in context: A236252 A232262 A048255 * A091329 A261241 A345772
KEYWORD
nonn
AUTHOR
Paolo P. Lava, May 04 2018
EXTENSIONS
a(13)-a(27) from Giovanni Resta, May 04 2018
STATUS
approved

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Last modified June 12 10:35 EDT 2024. Contains 373331 sequences. (Running on oeis4.)