A transform of the Jacobsthal numbers.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =0a(5) =-3a(6) =-9a(7) =-18a(8) =-27a(9) =-27a(10) =0a(11) =81a(12) =243a(13) =486a(14) =729a(15) =729a(16) =0a(17) =-2187a(18) =-6561a(19) =-13122a(20) =-19683a(21) =-19683a(22) =0a(23) =59049a(24) =177147a(25) =354294a(26) =531441a(27) =531441a(28) =0a(29) =-1594323