A111682 a(n) = (2n)^(2n) - (2n-1)!*(3n)!/((n-1)!*(2n)!).

1, 76, 16416, 6798016, 4551356800, 4470007597056, 6043460975190016, 10752691472850927616, 24343005503622220775424, 68309311335401364275200000, 232660170298374017479641923584, 945435062625215546945374336843776, 4518267167605818050886037588752203776

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..100

Example

2^2 - 1*3 = 1 = a(1).
4^4 - 2*3*5*6 = 256 - 180 = 76 = a(2).
6^6 - 3*4*5*7*8*9 = 46656 - 30240 = 16416 = a(3).
8^8 - 4*5*6*7*9*10*11*12 = 16777216 - 9979200 = 6798016 = a(4).
...

Maple

a:=n->(2*n)^(2*n)-(2*n-1)!*(3*n)!/(n-1)!/(2*n)!: seq(a(n), n=1..13); # (Emeric Deutsch)

Mathematica

Table[(2n)^(2n)-(2n-1)!(3n)!/((n-1)!(2n)!), {n, 12}] (* Harvey P. Dale, Jul 06 2011 *)

Prog

(PARI) a(n)={(2*n)^(2*n) - (2*n-1)!*(3*n)!/((n-1)!*(2*n)!)} \\ Andrew Howroyd, Nov 09 2019

Crossrefs

Sequence in context: A289227 A028480 A229413 * A271242 A241878 A033521

Adjacent sequences: A111679 A111680 A111681 * A111683 A111684 A111685

Keyword

nonn

Author

Amarnath Murthy, Aug 16 2005

Extensions

More terms from Emeric Deutsch, Aug 27 2005

Terms a(12) and beyond from Andrew Howroyd, Nov 09 2019

Status

approved