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Search: id:A069133
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| A069133 |
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Centered 20-gonal (or icosagonal) numbers. |
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+0
6
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| 1, 21, 61, 121, 201, 301, 421, 561, 721, 901, 1101, 1321, 1561, 1821, 2101, 2401, 2721, 3061, 3421, 3801, 4201, 4621, 5061, 5521, 6001, 6501, 7021, 7561, 8121, 8701
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Equals binomial transform of [1, 20, 20, 0, 0, 0,...] - Gary W. Adamson (qntmpkt(AT)yahoo.com), Jun 13 2008
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LINKS
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E. Weisstein, Centered Polygonal Numbers
Index entries for sequences related to centered polygonal numbers
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FORMULA
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a(n) = 10n^2 - 10n + 1
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EXAMPLE
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a(5)=201 because 201 = 10*5^2 - 10*5 + 1 = 250 - 50 + 1.
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CROSSREFS
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Cf. A005448, A001844, A005891, A003215, A069099.
Sequence in context: A020148 A037305 A051873 this_sequence A124714 A126375 A081302
Adjacent sequences: A069130 A069131 A069132 this_sequence A069134 A069135 A069136
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KEYWORD
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easy,nice,nonn
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AUTHOR
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Terrel Trotter, Jr. (ttrotter(AT)telesal.net), Apr 07 2002
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