Triangle read by rows: T(n,k) = number of Ringel ladders of order n and genus k.

Terms

a(0) =2a(1) =14a(2) =2a(3) =38a(4) =24a(5) =2a(6) =70a(7) =184a(8) =2a(9) =118a(10) =648a(11) =256a(12) =2a(13) =198a(14) =1656a(15) =2240a(16) =2a(17) =342a(18) =3752a(19) =9728a(20) =2560a(21) =2a(22) =614a(23) =8152a(24) =31168a(25) =25600a(26) =2a(27) =1142a(28) =17544a(29) =86784