login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Number of n X n 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X (n+1) binary array having two adjacent 1's and two adjacent 0's, with rows and columns of the latter in lexicographically nondecreasing order.
0

%I #7 Apr 06 2020 00:29:17

%S 2,11,153,4917,366606,66730314,31357593706

%N Number of n X n 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X (n+1) binary array having two adjacent 1's and two adjacent 0's, with rows and columns of the latter in lexicographically nondecreasing order.

%C Diagonal of A227333.

%e Some solutions for n=4

%e ..0..0..0..0....0..0..1..0....0..1..1..1....0..0..1..0....0..1..1..0

%e ..0..0..0..0....1..1..0..0....1..0..1..1....0..0..1..0....0..1..1..0

%e ..1..0..1..0....0..1..0..0....0..0..1..1....1..0..1..0....1..0..1..1

%e ..0..1..0..0....0..0..0..0....0..1..0..0....1..0..0..1....0..0..1..0

%Y Cf. A227333.

%K nonn

%O 1,1

%A _R. H. Hardin_ Jul 07 2013