A232703
Numbers k that divide sigma(k) + sigma(k^2).
Original entry on oeis.org
1, 2, 185, 113125, 535350201, 71373089217, 82225037115, 156231750533, 268821356379
Offset: 1
Cf.
A000203 (sigma(n) = sum of divisors of n).
-
Select[Range[150000], Mod[Plus @@ DivisorSigma[1, {#, #^2}], #] == 0 &] (* Giovanni Resta, Jun 10 2016 *)
A232704
Numbers n such that sigma(n)+n divides sigma(n^2).
Original entry on oeis.org
84889, 376443, 1260615, 2703555, 4883751, 7551847, 8894695, 9387081, 10142181, 12600825, 39450985, 57924711, 72978693, 73534503, 166503105, 428777995, 563715879, 578643967, 583540893, 1181555907, 1598569785, 1779455211, 2917138191, 3078534559, 3318534361
Offset: 1
Cf.
A000203 (sigma(n) = sum of divisors of n).
-
for(n=1, 10^8, if(sigma(n^2)%(sigma(n)+n)==0, print1(n ", "))) \\ Donovan Johnson, Nov 30 2013
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