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A057552 a(n) = Sum_{k=0..n} C(2k+2,k). 18
1, 5, 20, 76, 286, 1078, 4081, 15521, 59279, 227239, 873885, 3370029, 13027729, 50469889, 195892564, 761615284, 2965576714, 11563073314, 45141073924, 176423482324, 690215089744, 2702831489824, 10593202603774, 41550902139550 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

FORMULA

G.f.: 1/2*(2*x+(1-4*x)^(1/2)-1)/(1-4*x)^(1/2)/x^2/(-1+x). - Vladeta Jovovic, Sep 10 2003

Recurrence: n*(n+2)*a(n) = (5*n^2+8*n+2)*a(n-1) - 2*(n+1)*(2*n+1)*a(n-2). - Vaclav Kotesovec, Oct 11 2012

a(n) ~ 2^(2*n+4)/(3*sqrt(Pi*n)). - Vaclav Kotesovec, Oct 11 2012

a(n) = Sum_{k=1..n+1} k*A000108(k) = Sum_{k=1..n+1} A001791(k) = (A000108(n+1) * (4*n + 6 - (n+2)*hypergeom([1,-n-1], [-n-1/2], 1/4]) - 1)/2.

a(n) = Sum_{k=1..n+1} Sum_{i=1..k} C(i+k-1,k). - Wesley Ivan Hurt, Sep 19 2017

MAPLE

a:= n->add(binomial(2*j+2, j), j=0..n): seq(a(n), n=0..24); # Zerinvary Lajos, Oct 25 2006

MATHEMATICA

Table[Sum[Binomial[2k+2, k], {k, 0, n}], {n, 0, 20}]

(* or *)

Table[SeriesCoefficient[1/2*(2*x+(1-4*x)^(1/2)-1)/(1-4*x)^(1/2)/x^2/(-1+x), {x, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Oct 11 2012 *)

Table[(CatalanNumber[n + 1] (4 n + 6 - (n + 2) Hypergeometric2F1[1, -n-1, -n-1/2, 1/4]) - 1)/2, {n, 0, 20}] (* Vladimir Reshetnikov, Oct 03 2016 *)

PROG

(PARI) a(n) = sum(k=0, n, binomial(2*k+2, k)); \\ Michel Marcus, Oct 04 2016

CROSSREFS

Cf. A000108, A001791.

Sequence in context: A061278 A000758 A005283 * A300918 A269708 A295347

Adjacent sequences:  A057549 A057550 A057551 * A057553 A057554 A057555

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Sep 07 2000

STATUS

approved

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Last modified November 15 08:58 EST 2019. Contains 329144 sequences. (Running on oeis4.)