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Search: id:A074874
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| A074874 |
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Numbers n such that phi(n + phi(n)) = sigma(n). |
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+0
2
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| 1, 3, 5, 11, 23, 55, 87, 123, 383, 501, 957, 1015, 3565, 3777, 5667, 6141, 9069, 11033, 13827, 27347, 35119, 44693, 55645, 91915
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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sigma(23) = 24 = phi(23 + 22) = phi(23 + phi(23), so 23 is a term of the sequence.
phi(87 + phi(87)) = phi(87 + 56) = 120 = sigma(87), so 87 is a member of the sequence.
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MATHEMATICA
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Select[Range[10^5], EulerPhi[ # + EulerPhi[ # ]] == DivisorSigma[1, # ] &]
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CROSSREFS
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Sequence in context: A094810 A139376 A074892 this_sequence A051439 A076051 A018116
Adjacent sequences: A074871 A074872 A074873 this_sequence A074875 A074876 A074877
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Sep 12 2002
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