2097156domain: NAppears in sequences(Smallest prime >= 2^n) + (largest prime <= 2^n).at n=20A092507a(n) = 2^n + 4.at n=21A140504a(0) = 4; for n >= 1, a(n) = 2^n + 4.at n=21A1465281/4 the number of (n+1) X 5 0..2 arrays with every 2 X 2 subblock having distinct clockwise edge differences.at n=40A209723