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A144390 a(n) = 3*n^2 - n - 1. 11
1, 9, 23, 43, 69, 101, 139, 183, 233, 289, 351, 419, 493, 573, 659, 751, 849, 953, 1063, 1179, 1301, 1429, 1563, 1703, 1849, 2001, 2159, 2323, 2493, 2669, 2851, 3039, 3233, 3433, 3639, 3851, 4069, 4293, 4523, 4759, 5001, 5249, 5503, 5763, 6029, 6301, 6579 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Sequence's original Name was "First bisection of A135370."
The partial sums of this sequence give A081437. - Leo Tavares, Dec 26 2021
LINKS
FORMULA
a(n+1) = a(n) + 6*n + 2; see A016933.
G.f.: x*(1+6*x-x^2)/(1-x)^3. a(n) = A049450(n)-1. - R. J. Mathar, Oct 24 2008
a(-n) = A144391(n). - Michael Somos, Mar 27 2014
E.g.f.: (3*x^2 + 2*x -1)*exp(x) + 1. - G. C. Greubel, Jul 19 2017
From Leo Tavares, Dec 26 2021: (Start)
a(n) = A003215(n) - 2*A005408(n). See Bounded Hexagons illustration.
a(n) = A016754(n-1) - A002378(n-2). (End)
a(n) = A003154(n) - A049451(n-1). - John Elias, Dec 22 2022
MAPLE
A144390:=n->3*n^2-n-1; seq(A144390(n), n=1..50); # Wesley Ivan Hurt, Mar 26 2014
MATHEMATICA
Table[3*n^2 -n -1 , {n, 0, 50}] (* G. C. Greubel, Jul 19 2017 *)
PROG
(Magma) [3*n^2-n-1: n in [1..60]]; // Vincenzo Librandi, Jun 14 2011
(PARI) a(n)=3*n^2-n-1 \\ Charles R Greathouse IV, Oct 07 2015
CROSSREFS
Cf. A081437 (partial sums).
Sequence in context: A054302 A147395 A302906 * A024843 A363161 A183453
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, Oct 25 2008
STATUS
approved

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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)