a(n) = 4*a(n-1) - 8*a(n-2), with a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =4a(3) =8a(4) =0a(5) =-64a(6) =-256a(7) =-512a(8) =0a(9) =4096a(10) =16384a(11) =32768a(12) =0a(13) =-262144a(14) =-1048576a(15) =-2097152a(16) =0a(17) =16777216a(18) =67108864a(19) =134217728a(20) =0a(21) =-1073741824a(22) =-4294967296a(23) =-8589934592a(24) =0a(25) =68719476736a(26) =274877906944a(27) =549755813888a(28) =0