a(n) = 4*a(n-1) - 9*a(n-2), with a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =4a(3) =7a(4) =-8a(5) =-95a(6) =-308a(7) =-377a(8) =1264a(9) =8449a(10) =22420a(11) =13639a(12) =-147224a(13) =-711647a(14) =-1521572a(15) =318535a(16) =14968288a(17) =57006337a(18) =93310756a(19) =-139814009a(20) =-1399052840a(21) =-4337885279a(22) =-4760065556a(23) =20000705287a(24) =122843411152a(25) =311367297025a(26) =139878487732