A069854 Denominators of coefficients of expansion of sinh(x)/sin(x) (even powers only).

1, 3, 18, 1890, 22680, 1247400, 157172400, 6129723600, 81729648000, 127932046704000, 1646485441080480000, 37869165144851040000, 62372742591519360000, 9304453876089900528000000, 5075156659685400288000000, 4459030689216262044805920000000

Offset: 0

Author

Benoit Cloitre, May 03 2002

Keywords

• easy
• frac
• nonn

Examples

			G.f. = 1 + (1/3)*x^2 + (1/18)*x^4 + (13/1890)*x^6 + (17/22680)*x^8 + (97/1247400)*x^10 + ...
		

Links

• G. C. Greubel, Table of n, a(n) for n = 0..230

Crossrefs

Cf. A069853.

Programs

Magma

m:=60; R:=PowerSeriesRing(Rationals(), m);
b:= Coefficients(R!( Sinh(x)/Sin(x) ));
[Denominator( b[2*n-1] ): n in [1..Floor((m-2)/2)]]; // G. C. Greubel, Jan 31 2022

Maple

a:= n-> denom(coeff(series(sinh(x)/sin(x), x, 2*n+2), x, 2*n)):
seq(a(n), n=0..24);  # Alois P. Heinz, Feb 01 2022

Mathematica

With[{m=60}, CoefficientList[Series[Sinh[x]/Sin[x], {x, 0, m}], x]][[1 ;; ;;  2]]//Denominator (* G. C. Greubel, Jan 31 2022 *)

Sage

[denominator( ( sinh(x)/sin(x) ).series(x, 2*n+3).list()[2*n] ) for n in (0..60)] # G. C. Greubel, Jan 31 2022