A027881 a(i)=a(i-1)+a(j_1)*a(j_2) {where j_1+j_2=i-1, j_1 <= q j_2} + a(j_1)*a(j_2)*a(j_3) {where j_1+j_2+j_3=i-1, j_1 <= q j_2 <= q j_3} +...+ a(1)^{i-1}.

1, 1, 2, 4, 9, 20, 51, 121, 321, 826, 2186, 5789, 16114, 42449, 118281, 328425, 908933, 2510553, 7138324, 19869748

Offset: 1

Author

Dirk Kreimer (kreimer(AT)dipmza.physik.Uni-Mainz.DE)

Keywords

• nonn

Comments

At one time it was thought that this might be related to the Hopf algebra structure of perturbative Quantum Field Theory; this later proved not to be the case.

Possibly erroneous version of A093637. - Sean A. Irvine, Dec 09 2019

Links

• Dirk Kreimer, "On the Hopf algebra structure of perturbative quantum field theory"
• Dirk Kreimer, Home page