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
Examples
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.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Crossrefs
A037074 is a subsequence. - Amiram Eldar, Aug 08 2020
Programs
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Mathematica
Select[Range[2,464], IntegerQ[DivisorSigma[1,#]/Total[First/@FactorInteger[#]]] &] (* Jayanta Basu, May 16 2013 *)
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PARI
for(n=2,700,if(sigma(n)%sumdiv(n,d,isprime(d)*d)==0,print1(n,",")))