78855339domain: NAppears in sequencesa(n) = T(2*n+1,n), with T given by A027907.at n=11A027911T(n,[ n/2 ]), T given by A027907.at n=23A027913Number of n X 1 0..2 arrays with rows and columns in lexicographic nondecreasing order but with exactly three mistakes.at n=21A278365