cp's OEIS Frontend

A289987 Number of unlabeled connected loopless multigraphs with n nodes of degree less than n.

%I A289987 #42 Jun 02 2025 17:12:34
%S A289987 0,1,1,2,12,146,5847,716141,300635753,430472002801,2117649544384420,
%T A289987 36154420408979339192,2165755991529764630384554,
%U A289987 459803603042851200545393118005
%N A289987 Number of unlabeled connected loopless multigraphs with n nodes of degree less than n.
%C A289987 Multigraphs are loopless.
%e A289987 From _Gheorghe Coserea_, Oct 11 2017: (Start)
%e A289987 For n=4 the a(4)=12 solutions are:
%e A289987 o--o--o--o   o==o--o--o   o--o==o--o   o==o--o==o
%e A289987 o--o         o==o         o==o
%e A289987 |  |         |  |         |  |
%e A289987 o--o         o--o         o==o
%e A289987 o--o         o==o
%e A289987 | /          | /
%e A289987 |/           |/
%e A289987 o--o         o--o
%e A289987 o---o        o--o         o--o--o
%e A289987 |\ /|        | /|            |
%e A289987 | x |        |/ |            o
%e A289987 |/ \|        o--o
%e A289987 o---o
%e A289987 (End)
%o A289987 (nauty)  for n in {1..8}; do geng -c -D$[${n}-1] ${n} -q | multig -m$[${n}-1] -D$[${n}-1] -u; done
%Y A289987 A diagonal of A334546.
%Y A289987 Cf. A001349, A289988.
%K A289987 nonn,more
%O A289987 0,4
%A A289987 _Natan Arie Consigli_, Aug 19 2017
%E A289987 a(9)-a(13) from _Andrew Howroyd_, May 05 2020