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A065522 Numbers n such that sigma(n) and sigma(n+1) are nontrivial powers (A065496). 0
21, 93, 381, 1065, 1173, 5065, 5670, 5729, 6603, 8809, 10281, 15960, 17110, 39286, 40526, 47882, 49951, 61962, 85058, 85261, 99066, 117860, 125985, 126853, 135890, 143241, 171945, 179556, 185853, 208744, 209585, 210450, 251394, 261767, 288792 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..35.

MATHEMATICA

a = {}; Do[s = DivisorSigma[1, n]; If[ Position[ Union[ Transpose[ FactorInteger[s]] [[2]]], 1] != {{1}} && Union[ Mod[ Union[ Transpose[ FactorInteger[s]] [[2]]], Union[ Transpose[ FactorInteger[s]] [[2]]] [[1]]]] == {0}, a = Append[a, n]], {n, 2, 10^6} ]; a[[ Select[ Range[ Length[ a]], a[[ # ]] + 1 == a[[ # + 1 ]] & ]]]

CROSSREFS

Cf. A065496.

Sequence in context: A119109 A254603 A144856 * A218844 A219423 A123213

Adjacent sequences:  A065519 A065520 A065521 * A065523 A065524 A065525

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Nov 27 2001

STATUS

approved

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Last modified January 20 05:22 EST 2020. Contains 331067 sequences. (Running on oeis4.)