This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A172605 Number of 7*n X 2*n 0..1 arrays with row sums 2 and column sums 7 1
 1, 936369720, 1548539246648239560000, 259207529217195001892051045386944000, 1401029485328289844705736395976227319651581140480000, 122551057241825639587910301883432838920696717566795677090154147840000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Shanzhen Gao, Sequences Arising from Integer Matrix Enumeration (in preparation) [From Shanzhen Gao, Feb 16 2010] 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..14 FORMULA \frac{1}{(7!)^{2n}}\sum_{\gamma =0}^{2n}\sum_{\alpha =0}^{\min \{2n-\gamma,\lfloor (7n-\gamma )/2\rfloor \}}\sum_{\beta =0}^{\min \{2n-\gamma -\alpha,\lfloor (7n-\gamma -2\alpha )/3\rfloor \}}\frac{% (-1)^{\beta +\gamma }105^{\alpha +\beta }21^{\gamma }(2n)!(7n)!(\allowbreak 14n-4\alpha -6\beta -2\gamma )!}{\alpha !\beta !\gamma !(2n-\alpha -\beta -\gamma )!(7n-2\alpha -3\beta -\gamma )!2^{7n-2\alpha -3\beta -\gamma }} [From Shanzhen Gao, Feb 16 2010] CROSSREFS Sequence in context: A115385 A186805 A122532 * A015394 A114261 A168436 Adjacent sequences:  A172602 A172603 A172604 * A172606 A172607 A172608 KEYWORD nonn AUTHOR R. H. Hardin Feb 06 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .