G.f. A(x) satisfies A(A(A(A(x)))) = x + 16*x^2.

A141119

G.f. A(x) satisfies A(A(A(A(x)))) = x + 16*x^2.

Terms

    a(0) =1a(1) =4a(2) =-48a(3) =960a(4) =-23296a(5) =616448a(6) =-16830464a(7) =456228864a(8) =-11849367552a(9) =281940983808

External references