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A069173 Centered 22-gonal numbers. 6
1, 23, 67, 133, 221, 331, 463, 617, 793, 991, 1211, 1453, 1717, 2003, 2311, 2641, 2993, 3367, 3763, 4181, 4621, 5083, 5567, 6073, 6601, 7151, 7723, 8317, 8933, 9571 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Ivan Panchenko, Table of n, a(n) for n = 1..1000

E. Weisstein, Centered Polygonal Numbers

Index entries for sequences related to centered polygonal numbers

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = 11n^2 - 11n + 1.

a(n) = 22*n+a(n-1)-22 (with a(1)=1). - Vincenzo Librandi, Aug 08 2010

EXAMPLE

a(5) = 221 because 11*5^2 - 11*5 + 1 = 275 - 55 + 1 = 221

For n=2, a(2)=22*2+1-22=23; n=3, a(3)=22*3+23-22=67; n=4, a(4)=22*4+67-22=133.

MATHEMATICA

FoldList[#1 + #2 &, 1, 22 Range@ 45] (* Robert G. Wilson v, Feb 02 2011 *)

PROG

(PARI) a(n)=11*n^2-11*n+1 \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

Cf. centered polygonal numbers listed in A069190.

Sequence in context: A030458 A053559 A031376 * A124716 A139955 A126377

Adjacent sequences:  A069170 A069171 A069172 * A069174 A069175 A069176

KEYWORD

easy,nonn

AUTHOR

Terrel Trotter, Jr., Apr 09 2002

STATUS

approved

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Last modified November 18 05:25 EST 2017. Contains 294853 sequences.