a(n) = 3*a(n-1) - 6*a(n-2), with a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =3a(3) =3a(4) =-9a(5) =-45a(6) =-81a(7) =27a(8) =567a(9) =1539a(10) =1215a(11) =-5589a(12) =-24057a(13) =-38637a(14) =28431a(15) =317115a(16) =780759a(17) =439587a(18) =-3365793a(19) =-12734901a(20) =-18009945a(21) =22379571a(22) =175198383a(23) =391317723a(24) =122762871a(25) =-1979617725a(26) =-6675430401a(27) =-8148584853a(28) =15606827847a(29) =95711992659