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A154949 Diagonal sums of Riordan array A154948. 1
1, 1, 3, 5, 10, 18, 34, 62, 115, 211, 389, 715, 1316, 2420, 4452, 8188, 15061, 27701, 50951, 93713, 172366, 317030, 583110, 1072506, 1972647, 3628263, 6673417, 12274327, 22576008, 41523752, 76374088, 140473848, 258371689, 475219625 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..33.

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

FORMULA

G.f.: 1/((1-x^2)(1 - x - x^2 - x^3)).

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

a(n) = -A000035(n)/2 + A001590(n+4)/2. - R. J. Mathar, Oct 25 2012

MATHEMATICA

a=0; b=0; c=0; lst={}; Do[z=a+b+c+1; AppendTo[lst, z]; a=b; b=c; c=z; z=a+b+c; AppendTo[lst, z]; a=b; b=c; c=z, {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Feb 17 2010 *)

CROSSREFS

Sequence in context: A054179 A010049 A094986 * A318248 A107232 A134522

Adjacent sequences:  A154946 A154947 A154948 * A154950 A154951 A154952

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Jan 17 2009

STATUS

approved

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Last modified September 20 11:38 EDT 2021. Contains 347584 sequences. (Running on oeis4.)