A067244 Numbers k such that phi(k) divides (sigma(k+1) + sigma(k-1)).

2, 3, 4, 6, 32, 34, 54, 55, 58, 70, 84, 133, 141, 221, 285, 322, 377, 407, 472, 664, 684, 988, 1149, 1241, 1505, 1911, 1978, 2230, 2590, 2631, 2906, 2912, 3498, 6111, 6579, 7232, 8559, 11194, 13181, 13952, 15323, 15409, 15564, 17362, 18215, 18754, 22328

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[23000], Divisible[DivisorSigma[1, #-1]+DivisorSigma[1, #+1], EulerPhi[#]]&] (* Harvey P. Dale, Oct 04 2016 *)

Crossrefs

Cf. A000010, A000203.

Sequence in context: A065199 A249156 A033179 * A084811 A051856 A135236

Adjacent sequences: A067241 A067242 A067243 * A067245 A067246 A067247

Keyword

easy,nonn

Author

Benoit Cloitre, Feb 20 2002

Status

approved