Binomial transform of (-1)^mod(n,3) (A257075).

Terms

a(0) =1a(1) =0a(2) =0a(3) =2a(4) =6a(5) =12a(6) =22a(7) =42a(8) =84a(9) =170a(10) =342a(11) =684a(12) =1366a(13) =2730a(14) =5460a(15) =10922a(16) =21846a(17) =43692a(18) =87382a(19) =174762a(20) =349524a(21) =699050a(22) =1398102a(23) =2796204a(24) =5592406a(25) =11184810a(26) =22369620a(27) =44739242a(28) =89478486a(29) =178956972