p-INVERT of (1,1,1,1,1,...), where p(S) = 1 - 2 S - 2 S^3.

Terms

a(0) =2a(1) =6a(2) =20a(3) =68a(4) =230a(5) =774a(6) =2600a(7) =8732a(8) =29330a(9) =98526a(10) =330980a(11) =1111868a(12) =3735110a(13) =12547374a(14) =42150440a(15) =141596132a(16) =475664450a(17) =1597901526a(18) =5367837140a(19) =18032197268a(20) =60575633990a(21) =203491974774a(22) =683591422280