1098516domain: NAppears in sequencesa(1)=2; for n > 1, a(n) = 2^(n-2) + (1/(2n-2)) * Sum_{ d divides n-1 } phi(2d)*2^((n-1)/d).at n=21A216957Number of minimum dominating sets in the grid graph P_4 X P_n.at n=47A350822