%I #5 Aug 12 2016 07:04:20
%S 1,1,4,23,209,2301,29992,450525,7666097,145748085,3062086652,
%T 70451319403,1761725152737,47575849111097,1379912569740752,
%U 42782608276446713,1411969570132526241,49423093937535984041
%N Number of nX2 arrays containing 2 copies of 0..n-1 with no equal vertical or antidiagonal neighbors and new values introduced sequentially from 0.
%C Column 2 of A265679.
%e Some solutions for n=4
%e ..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
%e ..2..0....2..3....2..0....2..2....2..3....2..0....2..0....2..2....2..3....2..2
%e ..3..2....1..0....3..3....1..0....1..0....3..3....1..2....3..3....0..2....3..3
%e ..1..3....3..2....2..1....3..3....2..3....1..2....3..3....0..1....1..3....1..0
%Y Cf. A265679.
%K nonn
%O 1,3
%A _R. H. Hardin_, Dec 13 2015