OFFSET
1,2
COMMENTS
A matrix is Cantorian if no row matches any of the strings obtained by taking one term from each column in turn in such a way that they are from different rows. That is, no row word can match any transversal word.
More precisely, let the matrix be M = (M_ij). Then no row (M_i1, M_i2, ..., M_in) can agree with any "transversal" (M_{1, pi(1}}, ..., M_{n, pi{n}}) for any permutation pi in S_n.
REFERENCES
S. Brlek, M. Mendes France, J. M. Robson and M. Rubey, Cantorian tableaux and permanents, L'Enseignement Math. 50 (2004), 287-304.
EXAMPLE
a(2) = 4 because the matrices [[a,a],[b,b]], [[a,b],[b,a]] and the matrices obtained by switching a with b are Cantorian.
CROSSREFS
KEYWORD
hard,nonn,nice
AUTHOR
Jeffrey Shallit, Jun 14 2005
STATUS
approved