1/3 the number of (n+1)X4 0..2 arrays with every 2X2 subblock having at least two equal elements connected horizontally or vertically.

A184370

1/3 the number of (n+1)X4 0..2 arrays with every 2X2 subblock having at least two equal elements connected horizontally or vertically.

Terms

    a(0) =1107a(1) =49235a(2) =2167173a(3) =95528423a(4) =4210059673a(5) =185547841629

External references