A015791 - OEIS

A015791

a(n) is the smallest integer k such that phi(k) + n | sigma(k + n).

1, 2, 4, 7, 6, 1, 9, 3, 2, 65, 4, 50, 15, 156, 8, 60, 6, 80, 6, 15, 10, 126, 16, 49, 14, 33, 12, 1, 26, 60, 72, 51, 24, 103, 74, 10, 26, 69, 54, 97, 4, 200, 33, 9, 58, 105, 34, 89, 30, 144, 66, 175, 8, 83, 6, 123, 82, 15, 120, 1682, 42, 135, 58, 73, 30, 71, 10

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Muniru A Asiru, Table of n, a(n) for n = 0..102

MATHEMATICA

Array[Block[{k = 1}, While[Mod[DivisorSigma[1, k + #], EulerPhi[k] + #] != 0, k++]; k] &, 67, 0] (* Michael De Vlieger, Dec 10 2018 *)

PROG

(PARI) a(n) = {my(k=1); while(frac(sigma(k+n)/(eulerphi(k)+n)), k++); k; } \\ Michel Marcus, Dec 11 2018

CROSSREFS

Cf. A002110, A004394, A015775, A015781, A015782, A015783, A015784, A015785, A015786, A015788.

Sequence in context: A299324 A261076 A302991 * A335818 A129980 A198137