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

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =56a(5) =277a(6) =1449a(7) =7872a(8) =43978a(9) =251049a(10) =1457910a(11) =8585724a(12) =51152973a(13) =307770236a(14) =1867362978a(15) =11412645576a(16) =70194232585a(17) =434157164246