A076230 Numbers k such that sigma_2(k)/k and sigma_4(k)/k are integers.

1, 84, 435708, 986076, 1441188, 6066396, 7407036, 16763292, 18735444, 78863148, 260855028, 318502548, 1340673516, 3391115364, 10829086632, 45076171140, 45582899544, 57648961188, 77314641768, 128293717860, 149098104540, 174975241896, 440359518060, 461191689504

Offset

1,2

Links

Giovanni Resta, Table of n, a(n) for n = 1..41 (terms < 5*10^12)

Example

For k = 6066396, sigma_2(k)/k = 9156979, sigma_4(k)/k = 241153415598179286943.

Mathematica

Select[Range[10^7], And @@ Divisible[DivisorSigma[{2, 4}, #], #] &] (* Amiram Eldar, Jan 20 2020 *)

Prog

(PARI) isok(n) = !(sigma(n, 2) % n) && !(sigma(n, 4) % n); \\ Michel Marcus, Aug 28 2019
(Magma) [n: n in [1..10000000]|IsIntegral(DivisorSigma(2, n)/n) and IsIntegral(DivisorSigma(4, n)/n)]; // Marius A. Burtea, Aug 28 2019

Crossrefs

Intersection of A046762 and A046764.

Cf. A001157, A001159.

Sequence in context: A289557 A202580 A292196 * A118076 A056746 A111194

Adjacent sequences: A076227 A076228 A076229 * A076231 A076232 A076233

Keyword

nonn

Author

Labos Elemer, Oct 03 2002

Extensions

More terms from T. D. Noe, Apr 11 2006

a(11)-a(12) from Michel Marcus, Aug 28 2019

a(13)-a(18) from Amiram Eldar, Jan 20 2020

a(19)-a(24) from Giovanni Resta, Jan 21 2020

Status

approved