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A119574
a(n) = binomial(2*n,n)*(n+2)^2/(n+1).
1
4, 9, 32, 125, 504, 2058, 8448, 34749, 143000, 588302, 2418624, 9934834, 40770352, 167152500, 684656640, 2801810205, 11455885080, 46801769190, 191055480000, 779363066790, 3177034283280, 12942655253580, 52693956656640, 214412258531250, 871975203591024
OFFSET
0,1
FORMULA
Conjectured g.f.: (-1 + 14*x - 36*x^2 + (1 - 4*x)^(3/2))/(2*x*(1 - 4*x)^(3/2)). - Harvey P. Dale, Jun 02 2024.
The conjecture is true (see links). - Sela Fried, Oct 02 2024.
a(n) = A000108(n)*A000290(n+2). - Alois P. Heinz, Oct 02 2024
a(n) ~ 4^n * sqrt(n/Pi). - Amiram Eldar, Sep 20 2025
MAPLE
[seq (binomial(2*n, n)*(n+2)^2/(n+1), n=0..25)];
MATHEMATICA
Table[Binomial[2n, n] (n+2)^2/(n+1), {n, 0, 30}] (* Harvey P. Dale, Jun 02 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zerinvary Lajos, May 31 2006
STATUS
approved