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A152744 7 times pentagonal numbers: 7n(3n-1)/2. 3
0, 7, 35, 84, 154, 245, 357, 490, 644, 819, 1015, 1232, 1470, 1729, 2009, 2310, 2632, 2975, 3339, 3724, 4130, 4557, 5005, 5474, 5964, 6475, 7007, 7560, 8134, 8729, 9345, 9982, 10640, 11319, 12019, 12740, 13482, 14245, 15029 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Ivan Panchenko, Table of n, a(n) for n = 0..1000

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

FORMULA

a(n) = (21n^2 - 7n)/2 = A000326(n)*7.

a(n) = a(n-1)+21*n-14 (with a(0)=0). - Vincenzo Librandi, Nov 26 2010

G.f.: 7*x*(1+2*x)/(1-x)^3. - Colin Barker, Feb 14 2012

a(0)=0, a(1)=7, a(2)=35, a(n)=3*a(n-1)-3*a(n-2)+a(n-3). - Harvey P. Dale, Aug 08 2013

MATHEMATICA

s=0; lst={s}; Do[s+=n; AppendTo[lst, s], {n, 7, 7!, 21}]; lst (* Vladimir Joseph Stephan Orlovsky, Apr 03 2009 *)

Table[7n (3n-1)/2, {n, 0, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 7, 35}, 50] (* Harvey P. Dale, Aug 08 2013 *)

PROG

(PARI) a(n)=7*n*(3*n-1)/2 \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

Cf. A000326, A014642, A152743.

Sequence in context: A061825 A077536 A256391 * A169607 A130884 A037092

Adjacent sequences:  A152741 A152742 A152743 * A152745 A152746 A152747

KEYWORD

easy,nonn

AUTHOR

Omar E. Pol, Dec 12 2008

STATUS

approved

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Last modified November 18 05:08 EST 2017. Contains 294853 sequences.