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A081272
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Downward vertical of triangular spiral in A051682.
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2
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1, 25, 85, 181, 313, 481, 685, 925, 1201, 1513, 1861, 2245, 2665, 3121, 3613, 4141, 4705, 5305, 5941, 6613, 7321, 8065, 8845, 9661, 10513, 11401, 12325, 13285, 14281, 15313, 16381, 17485, 18625, 19801, 21013, 22261, 23545, 24865, 26221, 27613
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Reflection of A081271 in the horizontal A051682.
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FORMULA
| a(n)=C(n, 0)+24C(n, 1)+36C(n, 2); binomial transform of (1, 24, 36, 0, 0, 0, .....). a(n)=18n^2+6n+1. G.f.(1+22x+13x^2)/(1-x)^3.
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CROSSREFS
| Cf. A062741.
Sequence in context: A157530 A069232 A166080 * A027026 A087240 A044212
Adjacent sequences: A081269 A081270 A081271 * A081273 A081274 A081275
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Mar 15 2003
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