The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #4 Oct 29 2023 20:27:09
%S 0,0,2,18,156,1560,18600,262080,4284000,79833600,1671788160,
%T 38878963200,994367404800,27741377664000,838406080512000,
%U 27287153858764800,951529253875200000,35392677532692480000,1398727294865252352000,58529661706809925632000,2585234639710708457472000
%N Expansion of e.g.f. -log(1 - x^2/(1-x)^3).
%C a(n) is the number of ways to choose two elements from each branch of labeled octupi with n nodes.
%C A328055(n) is the corresponding sequence if we choose one element only.
%Y Cf. A029767, A328055.
%K nonn
%O 0,3
%A _Enrique Navarrete_, Oct 29 2023