Expansion of e.g.f. (1 - x - x^2)^x.

Terms

a(0) =1a(1) =0a(2) =-2a(3) =-9a(4) =-20a(5) =-30a(6) =66a(7) =0a(8) =-7216a(9) =-155736a(10) =-2447640a(11) =-40095000a(12) =-696155448a(13) =-13193809200a(14) =-269899395024