Numerator of the fraction tan( Sum_{k=1..n} arctan(k) ).

Terms

a(0) =1a(1) =-3a(2) =0a(3) =4a(4) =-9a(5) =105a(6) =-308a(7) =36a(8) =-423a(9) =2387a(10) =-26004a(11) =104472a(12) =-50617a(13) =119889a(14) =-5466072a(15) =3154072a(16) =51692571a(17) =-2921193a(18) =351666136a(19) =-1278405156a(20) =11188330461a(21) =-68445012691a(22) =553299094188