A086891 Denominator of 4*(Integral_{x=0..1} (1-x^2)^((2n-1)/2) dx)/Pi.

1, 4, 8, 64, 640, 2560, 35840, 114688, 688128, 13762560, 14417920, 346030080, 1799356416, 2399141888, 23991418880, 767725404160, 2372969431040, 5695126634496, 216414812110848, 221963909857280, 9322484214005760

Offset: 1

Author

Al Hakanson (hawkuu(AT)excite.com), Sep 18 2003

Keywords

• frac
• nonn

Examples

			a(2)=4.
		

Crossrefs

Cf. A076729 and A087547.

Programs

Mathematica

f[n_] := Denominator[ 3Simplify[ Sqrt[2]((Integrate[(1 + x^2)^((2n - 1)/2), {x, 0, 1}]) - (2n - 1)!!ArcSinh[1]/(2n)!!)]]; Table[ f[n], {n, 1, 21}] (* Robert G. Wilson v, Feb 27 2004 *)

Extensions

More terms from Robert G. Wilson v, Feb 27 2004