Expansion of bracket function.

Terms

a(0) =1a(1) =-3a(2) =6a(3) =-9a(4) =9a(5) =0a(6) =-27a(7) =81a(8) =-162a(9) =243a(10) =-243a(11) =0a(12) =729a(13) =-2187a(14) =4374a(15) =-6561a(16) =6561a(17) =0a(18) =-19683a(19) =59049a(20) =-118098a(21) =177147a(22) =-177147a(23) =0a(24) =531441a(25) =-1594323a(26) =3188646a(27) =-4782969a(28) =4782969a(29) =0