Powers of -2: a(n) = (-2)^n.

Terms

a(0) =1a(1) =-2a(2) =4a(3) =-8a(4) =16a(5) =-32a(6) =64a(7) =-128a(8) =256a(9) =-512a(10) =1024a(11) =-2048a(12) =4096a(13) =-8192a(14) =16384a(15) =-32768a(16) =65536a(17) =-131072a(18) =262144a(19) =-524288a(20) =1048576a(21) =-2097152a(22) =4194304a(23) =-8388608a(24) =16777216a(25) =-33554432a(26) =67108864a(27) =-134217728a(28) =268435456a(29) =-536870912