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A112087 4*(n^2 - n + 1). 4
4, 12, 28, 52, 84, 124, 172, 228, 292, 364, 444, 532, 628, 732, 844, 964, 1092, 1228, 1372, 1524, 1684, 1852, 2028, 2212, 2404, 2604, 2812, 3028, 3252, 3484, 3724, 3972, 4228, 4492, 4764, 5044, 5332, 5628, 5932, 6244, 6564, 6892, 7228, 7572, 7924, 8284 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Diagonal of a number spiral.

LINKS

Table of n, a(n) for n=1..46.

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

FORMULA

Equals 4*A002061. - Robert G. Wilson v

a(n) = 8*n + a(n-1) - 8 (with a(1)=4). - Vincenzo Librandi, Nov 13 2010

EXAMPLE

..43.44.45.46.47.48.49.50...

..42.21.22.23.24.25.26.51...

..40.19..7..8..9.10.27.52...

..40.19..6..1..2.11.28....

..39.18..5..4..3.12.29

..38.17.16.15.14.13.30

..37.36.35.34.33.32.31

MATHEMATICA

Table[4(n^2 - n + 1), {n, 2, 47}] (* Robert G. Wilson v *)

PROG

(Maxima) makelist(4*n^2 - 4*n + 4, n, 1, 55); /* Martin Ettl, Oct 16 2012 */

(PARI) a(n)=4*(n^2-n+1) \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

Sequence in context: A278211 A192736 A109629 * A166019 A184633 A006000

Adjacent sequences:  A112084 A112085 A112086 * A112088 A112089 A112090

KEYWORD

nonn,easy

AUTHOR

Jenny X. Chen (pookahead(AT)gmail.com), Nov 28 2005

EXTENSIONS

Edited and extended by Robert G. Wilson v, Nov 29 2005

STATUS

approved

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Last modified December 17 04:09 EST 2017. Contains 296096 sequences.