Riordan array ((1-x)/(1+x), x/(1+x)^2).

Terms

a(0) =1a(1) =-2a(2) =1a(3) =2a(4) =-4a(5) =1a(6) =-2a(7) =9a(8) =-6a(9) =1a(10) =2a(11) =-16a(12) =20a(13) =-8a(14) =1a(15) =-2a(16) =25a(17) =-50a(18) =35a(19) =-10a(20) =1a(21) =2a(22) =-36a(23) =105a(24) =-112a(25) =54a(26) =-12a(27) =1a(28) =-2a(29) =49