a(n) = floor(2^|n-1|/2). Or: 1, 0, followed by powers of 2.

Terms

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