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A026773 T(2n-1,n-1), T given by A026769. Also T(2n+1,n+1), T given by A026780. 2
1, 4, 17, 76, 352, 1674, 8129, 40156, 201236, 1020922, 5234660, 27089726, 141335846, 742712598, 3927908193, 20891799036, 111688381228, 599841215226, 3234957053984, 17512055200470, 95125188934942, 518340392855286, 2832580291316092, 15520177744727766 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A006318(n) - A000108(n). G.f.: (sqrt(1-4*x)-sqrt(1-6*x+x^2))/(2*x)-1/2. - Vladeta Jovovic, Nov 23 2003

a(n) = sum{k=0..n, C(n+k+1, n+1)C(n+1, k)/(k+1)}; a(n) = sum{k=0..n+1, C(n+2, k)C(n+k, n+1)}/(n+2). - Paul Barry, May 19 2005

CROSSREFS

Sequence in context: A290914 A117439 A081910 * A081186 A239204 A005572

Adjacent sequences:  A026770 A026771 A026772 * A026774 A026775 A026776

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified February 22 16:26 EST 2019. Contains 320399 sequences. (Running on oeis4.)