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 A158058 a(n) = 16*n^2 - 2*n. 2
 14, 60, 138, 248, 390, 564, 770, 1008, 1278, 1580, 1914, 2280, 2678, 3108, 3570, 4064, 4590, 5148, 5738, 6360, 7014, 7700, 8418, 9168, 9950, 10764, 11610, 12488, 13398, 14340, 15314, 16320, 17358, 18428, 19530, 20664, 21830, 23028, 24258, 25520 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The identity (16*(n-1) + 15)^2 - (16*n^2 - 2*n)*4^2 = 1 can be written as A125169(n-1)^2 - a(n)*4^2 = 1. - Vincenzo Librandi, Feb 01 2012 Sequence found by reading the line from 14, in the direction 14, 60, ... in the square spiral whose vertices are the generalized decagonal numbers A074377. - Omar E. Pol, Nov 02 2012 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 E. J. Barbeau, Polynomial Excursions, Chapter 10: Diophantine equations (2010), pages 84-85 (row 15 in the first table at p. 85, case d(t) = t*(4^2*t-2)). Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA G.f.: x*(-14 - 18*x)/(x-1)^3. a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). MAPLE seq(16*n^2-2*n, n=1..40); # Nathaniel Johnston, Jun 26 2011 MATHEMATICA LinearRecurrence[{3, -3, 1}, {14, 60, 138}, 40] PROG (MAGMA) [16*n^2-2*n: n in [1..40]] (PARI) a(n) = 16*n^2-2*n. CROSSREFS Cf. A125169. Sequence in context: A062022 A277986 A261282 * A100171 A063492 A051799 Adjacent sequences:  A158055 A158056 A158057 * A158059 A158060 A158061 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Mar 12 2009 STATUS approved

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Last modified January 18 13:55 EST 2019. Contains 319271 sequences. (Running on oeis4.)