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A065522
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Numbers n such that sigma(n) and sigma(n+1) are nontrivial powers (A065496).
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0
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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; internal format)
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OFFSET
| 1,1
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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 ]] & ]]]
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CROSSREFS
| Cf. A065496.
Sequence in context: A143843 A119109 A144856 * A123213 A174084 A193218
Adjacent sequences: A065519 A065520 A065521 * A065523 A065524 A065525
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 27 2001
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