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A125201 8*n^2 - 7*n + 1. 2
2, 19, 52, 101, 166, 247, 344, 457, 586, 731, 892, 1069, 1262, 1471, 1696, 1937, 2194, 2467, 2756, 3061, 3382, 3719, 4072, 4441, 4826, 5227, 5644, 6077, 6526, 6991, 7472, 7969, 8482, 9011, 9556, 10117, 10694, 11287, 11896, 12521, 13162, 13819, 14492, 15181 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Central terms of the triangle in A125199.

Sequence found by reading the line from 2, in the direction 2, 19,..., in the square spiral whose vertices are the triangular numbers A000217. - Omar E. Pol, Sep 05 2011

LINKS

Arkadiusz Wesolowski, Table of n, a(n) for n = 1..1000

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

FORMULA

a(n) = 1 + A051870(n). - Omar E. Pol, Sep 05 2011

Contribution from Arkadiusz Wesolowski, Dec 25 2011: (Start)

a(1) = 2, a(n) = a(n-1) + 16*n - 15.

a(n) = 2*a(n-1) - a(n-2) + 16 with a(1) = 2 and a(2) = 19.

G.f.: (1 - x + 16*x^2)/(1 - x)^3. (End)

MATHEMATICA

Table[8*n^2 - 7*n + 1, {n, 44}] (* Arkadiusz Wesolowski, Feb 15 2012 *)

PROG

(MAGMA) [8*n^2-7*n+1:n in [1..44]]; [From Vincenzo Librandi, Dec 27 2010]

CROSSREFS

Sequence in context: A031911 A136685 A226489 * A215392 A140544 A204219

Adjacent sequences:  A125198 A125199 A125200 * A125202 A125203 A125204

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, Nov 24 2006

STATUS

approved

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Last modified November 26 11:14 EST 2014. Contains 250056 sequences.