132476domain: NAppears in sequencesNumber of n X 2 0..1 arrays with no 1 equal to more than three of its king-move neighbors, with the exception of exactly two elements.at n=9A282475a(n) = Sum_{k=0..n} 2^(n-k) * binomial(4*n+1,k) * binomial(4*n-k-1,n-k).at n=4A386864