A070222 Numbers k such that the sum of prime divisors of k divides the sum of divisors of k.

15, 20, 24, 35, 42, 54, 66, 72, 95, 98, 100, 104, 108, 110, 114, 119, 120, 126, 132, 135, 140, 143, 160, 168, 189, 195, 207, 209, 216, 220, 224, 258, 264, 270, 276, 287, 290, 294, 319, 322, 323, 351, 360, 363, 375, 377, 378, 384, 392, 432, 440, 456, 459, 464

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

The sum of divisors of 132 is sigma(132) = 336; prime divisors of 132 are 2,3,11 and (336)/(2+3+11) = 336/16 = 21 hence 132 is in the sequence.

Mathematica

Select[Range[2, 464], IntegerQ[DivisorSigma[1, #]/Total[First/@FactorInteger[#]]] &] (* Jayanta Basu, May 16 2013 *)

Prog

(PARI) for(n=2, 700, if(sigma(n)%sumdiv(n, d, isprime(d)*d)==0, print1(n, ", ")))

Crossrefs

Cf. A000203, A008472.

A037074 is a subsequence. - Amiram Eldar, Aug 08 2020

Sequence in context: A322710 A316743 A014603 * A143321 A066860 A120159

Adjacent sequences: A070219 A070220 A070221 * A070223 A070224 A070225

Keyword

easy,nonn

Author

Benoit Cloitre, May 07 2002

Status

approved