Bi-diagonal inverse of (3n)!/(3k)!.

Terms

a(0) =1a(1) =-6a(2) =1a(3) =0a(4) =-120a(5) =1a(6) =0a(7) =0a(8) =-504a(9) =1a(10) =0a(11) =0a(12) =0a(13) =-1320a(14) =1a(15) =0a(16) =0a(17) =0a(18) =0a(19) =-2730a(20) =1a(21) =0a(22) =0a(23) =0a(24) =0a(25) =0a(26) =-4896a(27) =1a(28) =0a(29) =0