a(n) = 3*a(n-1) - 9*a(n-2), with a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =3a(3) =0a(4) =-27a(5) =-81a(6) =0a(7) =729a(8) =2187a(9) =0a(10) =-19683a(11) =-59049a(12) =0a(13) =531441a(14) =1594323a(15) =0a(16) =-14348907a(17) =-43046721a(18) =0a(19) =387420489a(20) =1162261467a(21) =0a(22) =-10460353203a(23) =-31381059609a(24) =0a(25) =282429536481a(26) =847288609443a(27) =0a(30) =0