OFFSET
1,5
COMMENTS
x(n) = tan( sum_{k=1..n} arctan(k)): see A180657.
LINKS
EXAMPLE
The x(n) sequence begins 1, -3, 0, 4, -9/19, 105/73, -308/331, 36/43, -423/281, 2387/4511, -26004/10873, ...
MAPLE
MATHEMATICA
x[n_] := x[n] = If[n == 1, 1, (x[n-1] + n)/(1 - n*x[n-1])];
a[n_] := Denominator[x[n]];
Table[a[n], {n, 1, 29}] (* Jean-François Alcover, Aug 09 2023 *)
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Dec 22 2012
STATUS
approved