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A143927 G.f. satisfies: A(x) = [1 + x*A(x) + x^2*A(x)^2]^2. 7
1, 2, 7, 28, 123, 572, 2769, 13806, 70414, 365636, 1926505, 10273870, 55349155, 300783420, 1646828655, 9075674700, 50304255210, 280248358964, 1568399676946, 8813424968192, 49709017472751, 281306750922072, 1596802663432503 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Vladimir Kruchinin, D. V. Kruchinin, Composita and their properties, arXiv:1103.2582 [math.CO], 2011-2013.

FORMULA

Self-convolution of A006605.

Bisection of A143926.

a(n) = ((24*n+12)*A006605(n)+(3*n+5)*A006605(n+1))/(13*n+17). - Mark van Hoeij, Jul 14 2010

a(n) = 1/(n+1)*Sum_{j=0..(2*n+2)} (binomial(j,2*j-3*n-4)*binomial(2*n+2 ,j)). - Vladimir Kruchinin, Dec 24 2010

a(n) = GegenbauerPoly(n,-2n-2,-1/2)/(n+1). - Emanuele Munarini, Oct 20 2016

a(n) = T(2*n+2, n)/(n+1), where T(n,k) = A027907(n,k). - Emanuele Munarini, Oct 20 2016

MATHEMATICA

Table[GegenbauerC[n, -2n-2, -1/2]/(n+1), {n, 0, 12}] (* Emanuele Munarini, Oct 20 2016 *)

n = 20;

A = Sum[a[k] x^k, {k, 0, n}] + x O[x]^n;

Table[a[k], {k, 0, n}] /. Reverse[Solve[LogicalExpand[(1 + x A + x^2 A^2)^2 == A]]] (* Emanuele Munarini, Oct 20 2016 *)

PROG

(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(i=0, n, A=(1+x*A+x^2*A^2)^2); polcoeff(A, n)}

(Maxima) makelist(ultraspherical(n, -2*n-2, -1/2)/(n+1), n, 0, 12); /* Emanuele Munarini, Oct 20 2016 */

CROSSREFS

Cf. A006605, A143926.

Sequence in context: A005435 A291091 A215973 * A253787 A060379 A002931

Adjacent sequences:  A143924 A143925 A143926 * A143928 A143929 A143930

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Sep 08 2008

STATUS

approved

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Last modified January 27 15:07 EST 2022. Contains 350607 sequences. (Running on oeis4.)