G.f. A(x) satisfies: A(x)^7 = A(x^7) / (1 - 7*x).

Terms

a(0) =1a(1) =1a(2) =4a(3) =20a(4) =110a(5) =638a(6) =3828a(7) =23515a(8) =146968a(9) =930797a(10) =5957100a(11) =38450370a(12) =249927394a(13) =1634140604a(14) =10738638021a(15) =70875009760a(16) =469546933535