OFFSET
1,2
REFERENCES
Gao, Shanzhen, and Matheis, Kenneth, Closed formulas and integer sequences arising from the enumeration of (0,1)-matrices with row sum two and some constant column sums. In Proceedings of the Forty-First Southeastern International Conference on Combinatorics, Graph Theory and Computing. Congr. Numer. 202 (2010), 45-53.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..11
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 06 2010
EXTENSIONS
Incorrect formula removed by Jon E. Schoenfield, Jan 22 2018
STATUS
approved