223079domain: NAppears in sequencesa(n) = 1 + Sum_{i=1..n} S2(i)*2^i, where S2(n) is digit sum of n, n in binary notation.at n=15A135570Number of (4+2) X (n+2) 0..3 arrays with every 3 X 3 subblock row and diagonal sum equal to 0 3 5 6 or 7 and every 3 X 3 column and antidiagonal sum not equal to 0 3 5 6 or 7.at n=21A252388