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A184974
Number of connected 7-regular simple graphs on 2n vertices with girth exactly 4.
7
0, 0, 0, 0, 0, 0, 0, 1, 1, 8, 741, 2887493
OFFSET
0,10
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).
Sequence in context: A058921 A240283 A181153 * A060183 A262353 A268148
KEYWORD
nonn,more,hard
AUTHOR
Jason Kimberley, Feb 28 2011
STATUS
approved