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A366953
Expansion of e.g.f. -log(1 - x^2/(1-x)^3).
0
0, 0, 2, 18, 156, 1560, 18600, 262080, 4284000, 79833600, 1671788160, 38878963200, 994367404800, 27741377664000, 838406080512000, 27287153858764800, 951529253875200000, 35392677532692480000, 1398727294865252352000, 58529661706809925632000, 2585234639710708457472000
OFFSET
0,3
COMMENTS
a(n) is the number of ways to choose two elements from each branch of labeled octupi with n nodes.
A328055(n) is the corresponding sequence if we choose one element only.
CROSSREFS
Sequence in context: A363568 A191814 A350569 * A052838 A052876 A121933
KEYWORD
nonn
AUTHOR
Enrique Navarrete, Oct 29 2023
STATUS
approved