1/3 the number of (n+1)X(n+1) 0..2 arrays with every 2X2 subblock having at least two equal elements connected horizontally or vertically.

A184367

1/3 the number of (n+1)X(n+1) 0..2 arrays with every 2X2 subblock having at least two equal elements connected horizontally or vertically.

Terms

    a(0) =21a(1) =2755a(2) =2167173a(3) =10378244309

External references