G.f. A(x) satisfies: the sum of the coefficients of x^k, k=0..n, in A(x)^n equals (3*n)!/n!^3, which is de Bruijn's sequence S(3,n) (A006480), for n>=0.

A232683

G.f. A(x) satisfies: the sum of the coefficients of x^k, k=0..n, in A(x)^n equals (3*n)!/n!^3, which is de Bruijn's sequence S(3,n) (A006480), for n>=0.