%I #6 Apr 20 2020 19:48:23
%S 1,2,18,1094,637358,4617638834,517992936833258,1088597786720842334698,
%T 50735031335891092927048172910,60946941227979732761779089927221771422
%N Number of n X n nonnegative integer arrays with new values introduced in each row and column in sequential order starting with zero.
%C Diagonal of A268079.
%e Some solutions for n=4
%e ..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
%e ..0..0..0..0....0..0..1..1....0..1..0..0....0..1..0..0....0..1..0..0
%e ..0..0..0..0....0..1..0..1....0..0..1..1....0..0..0..1....0..1..0..1
%e ..0..1..0..0....0..1..1..2....0..1..0..0....0..0..0..0....0..1..1..0
%Y Cf. A268079.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 25 2016