Riordan array ((1+x)/(1-x),x/(1+x)).

Terms

a(0) =1a(1) =2a(2) =1a(3) =2a(4) =1a(5) =1a(6) =2a(7) =1a(8) =0a(9) =1a(10) =2a(11) =1a(12) =1a(13) =-1a(14) =1a(15) =2a(16) =1a(17) =0a(18) =2a(19) =-2a(20) =1a(21) =2a(22) =1a(23) =1a(24) =-2a(25) =4a(26) =-3a(27) =1a(28) =2a(29) =1