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Search: id:A101303
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| 3, 7, 28, 60, 360, 1512, 3276, 16256, 65528, 261120, 79360, 1098240, 13852800, 25261824, 79536128, 1040179456, 1710858240, 13815410400, 71687577600, 137707384824, 151060010112, 1932916285440, 4212741841200, 508764077015040
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(1)= 3 = sigma(2)
a(2)= 7 = sigma(sigma(3))
a(3)= 28 = sigma(sigma(sigma(5)))
a(4)= 60 = sigma(sigma(sigma(sigma(7))))
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MATHEMATICA
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f[n_] := DivisorSigma[1, n]; Table[ Nest[f, Prime[n], n], {n, 25}] (from Robert G. Wilson v Dec 22 2004)
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CROSSREFS
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Cf. A090896.
Sequence in context: A062795 A062363 A136580 this_sequence A148751 A148752 A148753
Adjacent sequences: A101300 A101301 A101302 this_sequence A101304 A101305 A101306
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KEYWORD
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nonn,easy
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AUTHOR
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Jorge Coveiro (jorgecoveiro(AT)yahoo.com), Dec 22 2004
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 22 2004
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