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Number of unlabeled Hugenholz diagrams with n nodes.
2

%I #16 Jun 17 2022 16:05:14

%S 1,1,12,148,3150,90075,3431015,167013000,10129020300

%N Number of unlabeled Hugenholz diagrams with n nodes.

%C Hugenholz diagrams are a way of expressing terms in the quantum mechanical many-body perturbation theory.

%D P. D. Stevenson, "Automatic Generation of Vacuum Amplitude Many-Body Perturbation Series", Int. J. Mod. Phys. C 14, 1135 (2003)

%D A. Szabo and N. Ostlund, Modern Quantum Chemistry, Dover Publications, New York, 1996

%H Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a057/A057572.java">Java program</a> (github)

%Y Cf. A064732.

%K hard,more,nonn

%O 2,3

%A _Paul Stevenson_, Nov 28 2000

%E Offset corrected and a(9)-a(10) from _Sean A. Irvine_, Jun 17 2022