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A144391
a(n) = 3*n^2 + n - 1.
10
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
OFFSET
1,1
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
a(n) = A003215(n) - (n+1)*2. - Leo Tavares, Jul 04 2021
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
Sequence in context: A042269 A049043 A031378 * A024836 A227541 A023553
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