a(1)=0; a(n) = b(n) - Sum_{r=1..n-1} a(r)*b(n-1-r), where b(n) = A000085(n).

A201687

a(1)=0; a(n) = b(n) - Sum_{r=1..n-1} a(r)*b(n-1-r), where b(n) = A000085(n).

Terms

    a(0) =0a(1) =2a(2) =2a(3) =6a(4) =14a(5) =44a(6) =134a(7) =462a(8) =1616a(9) =6062a(10) =23306a(11) =93996a(12) =389102a(13) =1671158a(14) =7360256a(15) =33418374a(16) =155359922a(17) =741476492a(18) =3617591462a(19) =18065875422a(20) =92087408048a(21) =479382896030

External references