E.g.f. log(1 + sin(arctan(x))).

Terms

a(0) =0a(1) =1a(2) =-1a(3) =-1a(4) =6a(5) =9a(6) =-120a(7) =-225a(8) =5040a(9) =11025a(10) =-362880a(11) =-893025a(12) =39916800a(13) =108056025a(14) =-6227020800a(15) =-18261468225