1/4 the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having at least two equal elements connected horizontally or vertically.

A184145

1/4 the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having at least two equal elements connected horizontally or vertically.

Terms

    a(0) =43a(1) =499a(2) =5695a(3) =65227a(4) =746503a(5) =8544883a(6) =97806031a(7) =1119511003a(8) =12814167895a(9) =146673819139

External references