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A168452 Self-convolution of A005568, where A005568(n) is the product of two successive Catalan numbers C(n)*C(n+1). 6
1, 4, 24, 180, 1556, 14840, 152092, 1646652, 18613664, 217852008, 2623657384, 32361812912, 407342311632, 5217211974832, 67836910362772, 893766246630572, 11913422912188432, 160450066324972472, 2181014117345997704, 29894260817385950064, 412839378639052110464 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..500

FORMULA

G.f.: A(x) = (1/x)*Series_Reversion(x/G(x)^2) where G(x) = g.f. of A004304, where A004304(n) is the number of planar tree-rooted maps with n edges.

G.f.: A(x) = G(x*A(x))^2 where A(x/G(x)^2) = G(x)^2 where G(x) = g.f. of A004304.

a(n) ~ c * 16^n / n^3, where c = 3.07968404... . - Vaclav Kotesovec, Sep 12 2014

EXAMPLE

G.f.: A(x) = 1 + 4*x + 24*x^2 + 180*x^3 + 1556*x^4 + 14840*x^5 +...

A(x)^(1/2) = 1 + 2*x + 10*x^2 + 70*x^3 + 588*x^4 + 5544*x^5 + 56628*x^6 +...+ A005568(n)*x^n +...

A(x) satisfies: A(x/G(x)^2) = G(x)^2 where G(x) = g.f. of A004304:

G(x) = 1 + 2*x + 2*x^2 + 6*x^3 + 28*x^4 + 160*x^5 + 1036*x^6 +...+ A004304(n)*x^n +...

G(x)^2 = 1 + 4*x + 8*x^2 + 20*x^3 + 84*x^4 + 456*x^5 + 2860*x^6 +...+ A168451(n)*x^n +...

MAPLE

a:= proc(n) option remember; `if`(n<3, [1, 4, 24][n+1],

      (12*n*(n+1)*(16*n^4+68*n^3+44*n^2-63*n-25) *a(n-1)

       -(3072*n^6+768*n^5-8448*n^4+1152*n^3+3264*n^2-288) *a(n-2)

       +1024*n*(n-1)*(n-2)*(2*n-1)*(2*n-3)*(4*n+1) *a(n-3)) /

      ((n+1)^2*(n+2)*(n+3)*(n+4)*(4*n-3)))

    end:

seq(a(n), n=0..25);  # Alois P. Heinz, Oct 20 2013

MATHEMATICA

c[n_] := CatalanNumber[n]*CatalanNumber[n+1]; a[n_] := ListConvolve[cc = Array[c, n+1, 0], cc][[1]]; Table[a[n], {n, 0, 25}] (* Jean-Fran├žois Alcover, Jan 22 2017 *)

PROG

(PARI) {a(n)=local(C_2=vector(n+1, m, (binomial(2*m-2, m-1)/m)*(binomial(2*m, m)/(m+1)))); polcoeff(Ser(C_2)^2, n)}

CROSSREFS

Cf. A168451, A004304, A005568, A000108, variant: A168358.

Sequence in context: A213591 A243689 A309637 * A061720 A197472 A152403

Adjacent sequences:  A168449 A168450 A168451 * A168453 A168454 A168455

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Nov 26 2009

EXTENSIONS

Typo in formula corrected by Paul D. Hanna, Nov 28 2009

STATUS

approved

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Last modified September 23 22:32 EDT 2020. Contains 337315 sequences. (Running on oeis4.)