Riordan array ((1-x+sqrt(1+6*x+x^2))/2, (sqrt(1+6*x+x^2)-x-1)/2).

Terms

a(0) =1a(1) =1a(2) =1a(3) =-2a(4) =-1a(5) =1a(6) =6a(7) =2a(8) =-3a(9) =1a(10) =-22a(11) =-6a(12) =10a(13) =-5a(14) =1a(15) =90a(16) =22a(17) =-38a(18) =22a(19) =-7a(20) =1a(21) =-394a(22) =-90a(23) =158a(24) =-98a(25) =38a(26) =-9a(27) =1a(28) =1806a(29) =394