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A067244 Numbers n such that phi(n) divides (sigma(n+1)+sigma(n-1)). 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..47.

MATHEMATICA

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

CROSSREFS

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

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Last modified August 13 02:05 EDT 2020. Contains 336441 sequences. (Running on oeis4.)