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A144390
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a(n) = 3*n^2 - n - 1.
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11
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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)
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OFFSET
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1,2
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COMMENTS
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Sequence's original Name was "First bisection of A135370."
The partial sums of this sequence give A081437. - Leo Tavares, Dec 26 2021
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Leo Tavares, Illustration: Bounded Hexagons
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
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a(n+1) = a(n) + 6*n + 2; see A016933.
a(n) = 3*n^2 - n - 1. - Paolo P. Lava, Oct 06 2008
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)
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MAPLE
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A144390:=n->3*n^2-n-1; seq(A144390(n), n=1..50); # Wesley Ivan Hurt, Mar 26 2014
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MATHEMATICA
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Table[3*n^2 -n -1 , {n, 0, 50}] (* G. C. Greubel, Jul 19 2017 *)
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PROG
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(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
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CROSSREFS
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Cf. A016933, A049450, A144391.
Cf. A003215, A005408, A016754, A002378.
Cf. A081437 (partial sums).
Sequence in context: A054302 A147395 A302906 * A024843 A183453 A296311
Adjacent sequences: A144387 A144388 A144389 * A144391 A144392 A144393
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KEYWORD
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nonn,easy
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AUTHOR
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Paul Curtz, Oct 02 2008
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EXTENSIONS
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Edited by R. J. Mathar, Oct 24 2008
More terms from Vladimir Joseph Stephan Orlovsky, Oct 25 2008
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STATUS
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approved
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