G.f. A(x) satisfies A(x) = 1 + x^3 * (A(x) / (1 - x))^4.

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =4a(5) =10a(6) =24a(7) =67a(8) =200a(9) =586a(10) =1704a(11) =5049a(12) =15232a(13) =46284a(14) =141240a(15) =433696a(16) =1340500a(17) =4164830a(18) =12993792a(19) =40697472a(20) =127941300a(21) =403561902a(22) =1276763096a(23) =4050430502a(24) =12882398456a(25) =41068966204a(26) =131211997496a(27) =420056152498