5913882532domain: NAppears in sequencesa(n) = Sum_{k=0..n} T(n, k), array T as in A047080.at n=37A047081Number of n X 2 0..3 arrays x(i,j) with each element horizontally or vertically next to at least one element with value (x(i,j)+1) mod 4, no adjacent elements equal, and upper left element zero.at n=19A231057