A028580 C_{n+1}*C_n*C_{n-1}^2*C_{n-2}^4*...*C_2^{2^(n-2)}, where C_k are the Catalan numbers (A000108).

1, 2, 10, 280, 235200, 173859840000, 98238542885683200000000, 32169371027674057560745102540800000000000000000, 3518552669874927170883258602839130084576857453953842493259776000000000000000000000000000000000

Offset

1,2

Comments

Essentially the same as A003047, which is the main entry. [From R. J. Mathar, Oct 23 2008]

References

D.-Z. Du and F. K. Hwang, Combinatorial Group Testing and Its Applications, World Scientific, 2nd ed., 2000; p. 36.

Links

Table of n, a(n) for n=1..9.

Formula

a(n) = 2*(2n-1)*a(n-1)^2/(n+1).

Mathematica

RecurrenceTable[{a[n] == 2*(2*n-1)*a[n-1]^2/(n+1), a[1]==1}, a, {n, 1, 10}] (* Vaclav Kotesovec, Mar 07 2019 *)
nxt[{n_, a_}]:={n+1, (4n+2) a^2/(n+2)}; NestList[nxt, {1, 1}, 9][[;; , 2]] (* Harvey P. Dale, Dec 06 2025 *)

Crossrefs

Cf. A003047, A000108.

Sequence in context: A215286 A260231 A003047 * A171873 A098706 A143249

Adjacent sequences: A028577 A028578 A028579 * A028581 A028582 A028583

Keyword

nonn,easy

Author

N. J. A. Sloane, May 22 2000

Extensions

More terms from James Sellers, May 22 2000

Status

approved