A015808 - OEIS

%I #12 Dec 11 2018 08:43:11

%S 1,6,2,12,6,4,14,9,22,26,6,8,24,20,10,45,15,58,14,117,21,74,24,16,12,

%T 52,22,169,30,40,26,68,39,18,20,289,42,3604,34,146,51,72,38,180,28,

%U 730,48,32,70,116,46,194,24,150,45,1632,115,104,120,226,78,80,58

%N k is the first integer such that phi(k) + n | sigma(k).

%t a[n_] := Module[{k = 1}, While[!Divisible[DivisorSigma[1, k], EulerPhi[k] + n], k++]; k]; Array[a, 30, 0] (* _Amiram Eldar_, Dec 10 2018 *)

%Y Cf. A015791.

%K nonn

%O 0,2

%A _Robert G. Wilson v_

%E a(1) corrected by _Sean A. Irvine_, Dec 10 2018