Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #38 Feb 14 2021 08:10:51
%S 1,39,793,2379,7137,76921,230763,692289,2076867,8329831,24989493,
%T 53695813,74968479,161087439,224905437,243762649,324863409,375870691,
%U 483262317,731287947,1127612073,1449786951,2094136707,2193863841,2631094837,3382836219,3606816823
%N Numbers k such that sigma(k^2) and Sum_{d|k} d*sigma(d) are both multiples of k.
%C Intersection of A069520 and A232354.
%C Can these numbers be characterized as the terms of A232354 which do not have a factor in {11, 1093, ...}? Is this A090814, or (a subsequence of) A126197?
%H Donovan Johnson, <a href="/A232067/b232067.txt">Table of n, a(n) for n = 1..70</a>
%t fQ[n_] := Mod[DivisorSigma[1, n^2], n] == 0 && Mod[DivisorSum[n, #*DivisorSigma[1, #] &], n] == 0; Select[Range[100000], fQ] (* _T. D. Noe_, Nov 25 2013 *)
%Y Cf. A000203, A069520, A232354.
%K nonn
%O 1,2
%A _M. F. Hasler_, Nov 24 2013