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A117285 Numbers n for which the cototient n-phi(n) is a pentagonal number. +0
1
1, 2, 3, 5, 7, 11, 13, 17, 18, 19, 20, 22, 23, 25, 29, 30, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 75, 79, 83, 89, 97, 101, 102, 103, 107, 109, 110, 113, 127, 131, 132, 137, 139, 140, 149, 151, 155, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 203, 211, 223 (list; graph; listen)
OFFSET

0,2

EXAMPLE

30 is in the sequence because 30-phi(30)=22, which is a pentagonal number.

CROSSREFS

Cf. A000326.

Adjacent sequences: A117282 A117283 A117284 this_sequence A117286 A117287 A117288

Sequence in context: A084111 A020625 A033633 this_sequence A100546 A117094 A117289

KEYWORD

nonn

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006

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Last modified October 13 18:37 EDT 2008. Contains 145008 sequences.


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