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Search: id:A081272
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A081272 Downward vertical of triangular spiral in A051682. +0
2
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; listen)
OFFSET

0,2

COMMENT

Reflection of A081271 in the horizontal A051682.

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.

CROSSREFS

Cf. A062741.

Sequence in context: A157530 A069232 A166080 this_sequence A027026 A087240 A044212

Adjacent sequences: A081269 A081270 A081271 this_sequence A081273 A081274 A081275

KEYWORD

easy,nonn

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Mar 15 2003

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Last modified December 17 13:29 EST 2009. Contains 170826 sequences.


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