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A124370

Expansion of 1/(1-2x^2-3x^3-x^4).

1, 0, 2, 3, 5, 12, 21, 42, 83, 159, 313, 609, 1186, 2316, 4512, 8799, 17158, 33450, 65225, 127173, 247958, 483471, 942660, 1837989, 3583691, 6987429, 13624009, 26563920, 51793996, 100987296, 196903761, 383920500

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OFFSET

0,3

COMMENTS

Diagonal sums of number triangle A124369.

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (0,2,3,1).

FORMULA

a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, C(j,n-k-j)*C((j+k)/2,(j-k)/2)*(1+(-1)^(j-k))/2}}

a(0)=1, a(1)=0, a(2)=2, a(3)=3, a(n)=2*a(n-2)+3*a(n-3)+a(n-4). - Harvey P. Dale, Feb 11 2015

MATHEMATICA

CoefficientList[Series[1/(1-2x^2-3x^3-x^4), {x, 0, 40}], x] (* or *) LinearRecurrence[{0, 2, 3, 1}, {1, 0, 2, 3}, 40] (* Harvey P. Dale, Feb 11 2015 *)

CROSSREFS

Sequence in context: A282237 A004689 A183364 * A003428 A191626 A030041

Adjacent sequences: A124367 A124368 A124369 * A124371 A124372 A124373

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Oct 27 2006

STATUS

approved

URL: https://oeis.org/A124370

⇱ A124370 - OEIS