9443362domain: NAppears in sequences1/16 the number of (n+1) X 4 0..3 arrays with all 2 X 2 subblocks having the same four values.at n=20A184033G.f. A(x) satisfies: A(x) = (1/(1 - x)) * A(x^2)^2*A(x^3)^3*A(x^4)^4* ... *A(x^k)^k* ...at n=26A307604