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 A144391 a(n) = 3*n^2 + n - 1. 9
 3, 13, 29, 51, 79, 113, 153, 199, 251, 309, 373, 443, 519, 601, 689, 783, 883, 989, 1101, 1219, 1343, 1473, 1609, 1751, 1899, 2053, 2213, 2379, 2551, 2729, 2913, 3103, 3299, 3501, 3709, 3923, 4143, 4369, 4601, 4839, 5083, 5333, 5589, 5851, 6119, 6393, 6673 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..3000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = A135370(2*n). First differences: a(n+1) - a(n) = A016957(n). a(n) - A144390(n) = 6*n + 4 = A005843(n). From R. J. Mathar, Oct 24 2008: (Start) G.f.: x*(3 + 4*x - x^2)/(1 - x)^3. a(n) = A049451(n) - 1. (End) E.g.f.: (3*x^2 + 4*x - 1)*exp(x) + 1. - G. C. Greubel, Jul 19 2017 a(n) = 1 + Sum_{i = n-1..2*n-1} 2*i. - Bruno Berselli, Feb 16 2018 MATHEMATICA Table[3 n^2 + n - 1, {n, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {3, 13, 29}, 50] (* Harvey P. Dale, Sep 18 2016 *) PROG (MAGMA) [3*n^2+n-1: n in [1..50]]; // Vincenzo Librandi, May 06 2011 (PARI) a(n)=3*n^2+n-1 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Cf. A135370, A144390. Sequence in context: A042269 A049043 A031378 * A024836 A227541 A023553 Adjacent sequences:  A144388 A144389 A144390 * A144392 A144393 A144394 KEYWORD nonn,easy AUTHOR Paul Curtz, Oct 02 2008 EXTENSIONS Edited by R. J. Mathar, Oct 24 2008 More terms from Vladimir Joseph Stephan Orlovsky, Mar 01 2009 STATUS approved

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Last modified October 13 20:38 EDT 2019. Contains 327981 sequences. (Running on oeis4.)