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A033569 (2*n - 1)*(3*n + 1). 2
-1, 4, 21, 50, 91, 144, 209, 286, 375, 476, 589, 714, 851, 1000, 1161, 1334, 1519, 1716, 1925, 2146, 2379, 2624, 2881, 3150, 3431, 3724, 4029, 4346, 4675, 5016, 5369, 5734, 6111, 6500, 6901, 7314, 7739, 8176, 8625, 9086, 9559, 10044, 10541, 11050, 11571 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

For n>0, a(n) is the sum of the numbers from 2n+2 to 4n. The last digit of a(n) corresponds to the last digit of the squares mod 10 (A008959). Binomial Transform of a(n) starts: -1, 3, 28, 124, 432, 1328, 3776, 10176, 26368, ... . - Wesley Ivan Hurt, Dec 06 2014

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

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

FORMULA

G.f.: (-1+7*x+6*x^2)/(1-x)^3. - Vincenzo Librandi, Jul 07 2012

a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - Vincenzo Librandi, Jul 07 2012

E.g.f.: (-1+5*x+6*x^2)*e^x. - Robert Israel, Dec 07 2014

MAPLE

A033569:=n->(2*n-1)*(3*n+1): seq(A033569(n), n=0..50); # Wesley Ivan Hurt, Dec 06 2014

MATHEMATICA

CoefficientList[Series[(-1+7*x+6*x^2)/(1-x)^3, {x, 0, 50}], x] (* Vincenzo Librandi, Jul 07 2012 *)

PROG

(MAGMA) [(2*n-1)*(3*n+1): n in [0..50]]; // Vincenzo Librandi, Jul 07 2012

CROSSREFS

Cf. A008959.

Sequence in context: A063122 A110737 A042223 * A201446 A220772 A242135

Adjacent sequences:  A033566 A033567 A033568 * A033570 A033571 A033572

KEYWORD

sign,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified June 30 12:56 EDT 2015. Contains 259077 sequences.