A184974 - OEIS

A184974

Number of connected 7-regular simple graphs on 2n vertices with girth exactly 4.

0, 0, 0, 0, 0, 0, 0, 1, 1, 8, 741, 2887493

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OFFSET

0,10

LINKS

FORMULA

a(n) = A186714(n,5) - A186715(n,5).

EXAMPLE

a(0)=0 because even though the null graph (on zero vertices) is vacuously 7-regular and connected, since it is acyclic, it has infinite girth.

The a(7)=1 graph is the complete bipartite graph K_{7,7}.

CROSSREFS

Connected k-regular simple graphs with girth exactly 4: A006924 (k=3), A184944 (k=4), A184954 (k=5), A184964 (k=6), this sequence (k=7).

Connected 7-regular simple graphs with girth at least g: A014377 (g=3), A181153 (g=4).

Connected 7-regular simple graphs with girth exactly g: A184973 (g=3), this sequence (g=4).

KEYWORD

nonn,more,hard

AUTHOR

STATUS

approved