OFFSET
0,13
COMMENTS
T(n,k) is the number of nonequivalent n X n binary matrices with k ones in every row and column up to permutation of rows. - Andrew Howroyd, Apr 18 2020
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..230 (rows 0..20)
P. A. MacMahon, Combinations derived from m identical sets of n different letters and their connexion with general magic squares, Proc. London Math. Soc., 17 (1917), 25-41.
FORMULA
T(n,k) = T(n,n-k). - Andrew Howroyd, Apr 18 2020
EXAMPLE
Triangle begins:
1;
1, 1;
1, 1, 1;
1, 1, 1, 1;
1, 1, 6, 1, 1;
1, 1, 22, 22, 1, 1;
1, 1, 130, 550, 130, 1, 1;
1, 1, 822, 16700, 16700, 822, 1, 1;
1, 1, 6202, 703297, 3330915, 703297, 6202, 1, 1;
...
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
N. J. A. Sloane, Jul 30 2015
EXTENSIONS
Extended to include k=0 and more terms added by Andrew Howroyd, Apr 18 2020
STATUS
approved