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

Terms

a(0) =1a(1) =4a(2) =10a(3) =36a(4) =155a(5) =704a(6) =3384a(7) =16844a(8) =86097a(9) =449344a(10) =2384170a(11) =12822556a(12) =69743953a(13) =382982940a(14) =2120323014a(15) =11822279232a(16) =66327376437a(17) =374162700460