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

Terms

a(0) =1a(1) =1a(2) =-2a(3) =9a(4) =-24a(5) =70a(6) =-720a(7) =5985a(8) =-39200a(9) =337176a(10) =-3628800a(11) =40907790a(12) =-479001600a(13) =6128488080a(14) =-87104969952