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A069178
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Centered 21-gonal numbers.
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1
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1, 22, 64, 127, 211, 316, 442, 589, 757, 946, 1156, 1387, 1639, 1912, 2206, 2521, 2857, 3214, 3592, 3991, 4411, 4852, 5314, 5797, 6301, 6826, 7372, 7939, 8527, 9136, 9766, 10417, 11089, 11782, 12496, 13231, 13987, 14764, 15562, 16381, 17221, 18082, 18964
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| E. Weisstein, Centered Polygonal Numbers
Index entries for sequences related to centered polygonal numbers
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
| a(n) = (21n^2 - 21n + 2)/2
a(n)=21*n+a(n-1)-21 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 08 2010]
G.f. -x*(1+19*x+x^2) / (x-1)^3. - R. J. Mathar, Feb 04 2011
Binomial transform of [1, 21, 21, 0, 0, 0,...] and Narayana transform (A001263) of [1, 21, 0, 0, 0,...]. - Gary W. Adamson, Jul 26 2011
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MATHEMATICA
| FoldList[#1 + #2 &, 1, 21 Range@ 45] (* Robert G. Wilson v, Feb 02 2011 *)
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CROSSREFS
| Cf. A005448, A001844, A005891, A003215, A069099, A069133, A069125 - A069132.
Sequence in context: A156797 A051874 A140390 * A081929 A124715 A126376
Adjacent sequences: A069175 A069176 A069177 * A069179 A069180 A069181
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KEYWORD
| easy,nonn
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AUTHOR
| Terrel Trotter, Jr. (ttrotter(AT)telesal.net), Apr 09 2002
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