A046841 - OEIS

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A046841

Numbers whose sum of divisors divides their sum of cubes of divisors.

1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 46, 47, 48, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85

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OFFSET

1,2

COMMENTS

A005117 (squarefree numbers) is a subsequence. - Ivan Neretin, Dec 20 2017

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Paolo P. Lava)

EXAMPLE

2 is a term because 1 + 8 = 9 is divisible by 1 + 2 = 3.

208 is a term: The power sums of divisors for k = 0, 1, 2, 3 are as follows: 10, 434, 54970, 10288838, and sigma(1,208) = 434 divides sigma(3,208) = 10288838 = 434*23707.

MATHEMATICA

Select[Range@ 85, Divisible[DivisorSigma[3, #], DivisorSigma[1, #]] &] (* Michael De Vlieger, Aug 01 2017 *)

PROG

(PARI) isA046841(n)=sigma(n, 3)%sigma(n, 1)==0 \\ Michael B. Porter, Apr 07 2010

CROSSREFS

Cf. A000203, A001158, A005117.

Cf. A003601, A020486.

Sequence in context: A175084 A171519 A072099 * A244218 A164514 A000037

Adjacent sequences: A046838 A046839 A046840 * A046842 A046843 A046844

KEYWORD

nonn

AUTHOR

Labos Elemer

STATUS

approved

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