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A006137 a(n) = 1 + n/2 + 9*n^2/2. 4
1, 6, 20, 43, 75, 116, 166, 225, 293, 370, 456, 551, 655, 768, 890, 1021, 1161, 1310, 1468, 1635, 1811, 1996, 2190, 2393, 2605, 2826, 3056, 3295, 3543, 3800, 4066, 4341, 4625, 4918, 5220, 5531, 5851, 6180 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3, -3, 1).

FORMULA

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3), with a(0)=1, a(1)=6 and a(2)=20. - Paolo P. Lava, Jul 17 2009

a(n) = a(n-1) + 9*n - 4 (with a(0)=1). - Vincenzo Librandi, Nov 18 2010

MATHEMATICA

s = 1; lst = {s}; Do[s += n + 4; AppendTo[lst, s], {n, 1, 350, 9}]; lst (* Zerinvary Lajos, Jul 11 2009 *)

Table[1+n/2+9 n^2/2, {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 6, 20}, 40] (* Harvey P. Dale, Oct 05 2012 *)

PROG

(PARI) a(n)=1+n/2+9*n^2/2 \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

Sequence in context: A094274 A094279 A093913 * A225269 A048969 A005564

Adjacent sequences:  A006134 A006135 A006136 * A006138 A006139 A006140

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified October 15 04:33 EDT 2019. Contains 328026 sequences. (Running on oeis4.)