774840980domain: NAppears in sequencesa(0)=4, a(n) = 3*a(n-1) - 4.at n=18A115099Total number of round trips, each of length 2*n on the graph P_5 (o-o-o-o-o).at n=18A198635a(0) = 0, a(1) = 2, a(2) = 1, and for any n > 2 with ternary representation n = Sum_{i=0..k} t_i * 3^i, a(n) = Sum_{i=0..k} a(t_i) * 3^a(i).at n=28A300956