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%I #6 Dec 09 2019 22:27:30
%S 1,1,2,4,9,20,51,121,321,826,2186,5789,16114,42449,118281,328425,
%T 908933,2510553,7138324,19869748
%N 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}.
%C 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.
%C Possibly erroneous version of A093637. - _Sean A. Irvine_, Dec 09 2019
%H Dirk Kreimer, <a href="http://arXiv.org/abs/q-alg/9707029">"On the Hopf algebra structure of perturbative quantum field theory"</a>
%H Dirk Kreimer, <a href="http://dipmza.physik.uni-mainz.de/~kreimer/homepage.html">Home page</a>
%K nonn
%O 1,3
%A Dirk Kreimer (kreimer(AT)dipmza.physik.Uni-Mainz.DE)
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