A114876 Let d(1)=1 and d(n) = d(n-1)*n^(2n-2)*(2n-1)^(3-2n). Then a(n)=numerator(d(n)).

1, 4, 108, 442368, 51200000, 52428800000, 43177371238400000, 60766747818779941065981952, 23542283154891408151173909109014528, 60268244876522004867005207319077191680000000000

Offset

1,2

Links

Table of n, a(n) for n=1..10.

Example

1, 4/3, 108/125, 442368/2100875, 51200000/2977309629, 52428800000/118890080527911, ...

Mathematica

d[1] = 1; d[n_] := d[n] = d[n - 1]*n^(2 n - 2)*(2 n - 1)^(3 - 2 n); a[n_] := Numerator[d[n]]; Array[a, 10] (* Amiram Eldar, Mar 04 2023 *)

Crossrefs

Cf. A114877 (denominator).

Sequence in context: A002109 A259373 A076265 * A037980 A240626 A297916

Adjacent sequences: A114873 A114874 A114875 * A114877 A114878 A114879

Keyword

easy,frac,nonn

Author

T. D. Noe, Jan 03 2006

Extensions

Edited by Michel Marcus, Mar 04 2023

Status

approved