64138178287domain: NAppears in sequencesa(0) = 0 and a(n) = (5*(-4)^n + 16*(-1)^n + 9*4^n)/240 for n >= 1.at n=20A113968a(0)=1, a(1)=2; for n>1, a(n)=3*a(n-1)+4*a(n-2)+5.at n=18A126019