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 A125201 a(n) = 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 linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = 1 + A051870(n). - Omar E. Pol, Sep 05 2011 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]]; // Vincenzo Librandi, Dec 27 2010 (PARI) a(n)=8*n^2-7*n+1 \\ Charles R Greathouse IV, Jun 17 2017 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 January 28 09:17 EST 2020. Contains 331318 sequences. (Running on oeis4.)