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A140960 a(n) = (2*(-1)^n - 2^(n+1) + 3*n*2^n)/9. 4
0, 0, 2, 6, 18, 46, 114, 270, 626, 1422, 3186, 7054, 15474, 33678, 72818, 156558, 334962, 713614, 1514610, 3203982, 6757490, 14214030, 29826162, 62448526, 130489458, 272163726, 566697074, 1178133390, 2445745266, 5070447502, 10498808946, 21713445774, 44858547314 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Specify that a triangle has T(n,0) = T(n,n) = A001045(n), and T(r,c) = T(r-1,c-1) + T(r-1,c). The sum of the terms in the first n rows is a(n+1). - J. M. Bergot, May 21 2013

a(n) is the difference between the total number of runs of equal parts in the compositions of n+1, and the compositions of n+1. - Gregory L. Simay, May 04 2017

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (3,0,-4)

FORMULA

a(n+1) - 2*a(n) = A078008(n+1) = 2*A001045(n).

G.f.: 2*x^2/((1+x)*(1-2*x)^2).

a(n) = 2*A045883(n-1).

a(n) = 3*a(n-1) - 4*a(n-3), n > 2.

a(n) = A059570(n+1) - A011782(n+1). - Gregory L. Simay, May 04 2017

MATHEMATICA

LinearRecurrence[{3, 0, -4}, {0, 0, 2}, 40] (* Harvey P. Dale, Apr 14 2015 *)

PROG

(MAGMA) [( 2*(-1)^n-2^(n+1)+3*n*2^n)/9: n in [0..40]]; // Vincenzo Librandi, Aug 08 2011

(PARI) a(n)=(2*(-1)^n-2^(n+1)+3*n*2^n)/9 \\ Charles R Greathouse IV, Oct 16 2015

CROSSREFS

Sequence in context: A308305 A054136 A232600 * A072827 A248169 A002529

Adjacent sequences:  A140957 A140958 A140959 * A140961 A140962 A140963

KEYWORD

nonn,easy

AUTHOR

Paul Curtz, Jul 26 2008

EXTENSIONS

Definition replaced with Lava's closed form of August 2008 by R. J. Mathar, Feb 11 2010

STATUS

approved

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Last modified July 23 13:49 EDT 2019. Contains 325254 sequences. (Running on oeis4.)