A003955 a(n) = (2*n + 4) * (1*3*5*...*(2*n+1))^2.

4, 54, 1800, 110250, 10716300, 1512784350, 292183491600, 73958946311250, 23749039426612500, 9430743556307823750, 4537044990907363935000, 2600104866872495148416250, 1750070583471871734510937500, 1366930130733208386919792968750, 1226227455943070136959515612500000

Offset

0,1

Links

G. C. Greubel, Table of n, a(n) for n = 0..222

Formula

Equals (2*n+4) * A001818(n+1).

Equals (n+2)!*(n+1)!*binomial(2*n+2, n+1)^2/2^(2*n+1). - G. C. Greubel, Sep 24 2019

Maple

seq((n+2)!*(n+1)!*binomial(2*n+2, n+1)^2/2^(2*n+1), n=0..20); # G. C. Greubel, Sep 24 2019

Mathematica

Table[(n+2)!*(n+1)!*Binomial[2*n+2, n+1]^2/2^(2*n+1), {n, 0, 20}] (* G. C. Greubel, Sep 24 2019 *)

Prog

(PARI) vector(21, n, (n+1)!*n!*binomial(2*n, n)^2/2^(2*n-1) ) \\ G. C. Greubel, Sep 24 2019
(Magma) F:=Factorial; [F(n+2)*F(n+1)*Binomial(2*n+2, n+1)^2/2^(2*n+1): n in [0..20]]; // G. C. Greubel, Sep 24 2019
(Sage) f=factorial; [f(n+2)*f(n+1)*binomial(2*n+2, n+1)^2/2^(2*n+1) for n in (0..20)] # G. C. Greubel, Sep 24 2019
(GAP) F:=Factorial;; List([0..20], n-> F(n+2)*F(n+1)*Binomial(2*n+2, n+1)^2/2^(2*n+1) ); # G. C. Greubel, Sep 24 2019

Crossrefs

Cf. A001818.

Sequence in context: A225823 A265004 A284747 * A182264 A355128 A355126

Adjacent sequences: A003952 A003953 A003954 * A003956 A003957 A003958

Keyword

nonn

Author

N. J. A. Sloane, Joe Keane (jgk(AT)jgk.org)

Extensions

More terms added by G. C. Greubel, Sep 24 2019

Status

approved