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 #6 Apr 28 2023 17:37:42
%S 1,3,1,7,1,12,1,15,1,3,1,28,1,3,1,31,1,39,1,22,1,3,1,60,1,3,1,7,1,12,
%T 1,63,1,3,1,91,1,3,1,50,1,33,1,7,1,3,1,124,1,3,1,7,1,120,1,15,1,3,1,
%U 43,1,3,1,127,1,12,1,7,1,3,1,195,1,3,1,7,1,12,1,106,1,3,1,140
%N a(n) = Sum_{d|n, phi(d)|n} d.
%t a[n_] := DivisorSum[n, # &, Divisible[n, EulerPhi[#]] &]; Array[a, 100]
%o (PARI) a(n) = sumdiv(n, d, if (!(n % eulerphi(d)), d)); \\ _Michel Marcus_, Apr 28 2023
%Y Cf. A000010 (phi), A069932, A362470.
%K nonn,easy
%O 1,2
%A _Wesley Ivan Hurt_, Apr 28 2023