Product_{n>=1} (1 + x^n)^(a(n)/n!) = 1 + arctan(x).

A354275

Product_{n>=1} (1 + x^n)^(a(n)/n!) = 1 + arctan(x).

Terms

    a(0) =1a(1) =0a(2) =-2a(3) =8a(4) =-16a(5) =-64a(6) =-832a(7) =13824a(8) =8192a(9) =-36096a(10) =-4228608a(11) =-58438656a(12) =-398991360a(13) =-3452915712a(14) =44581613568

External references