Catapolyoctagons (see Cyvin et al. for precise definition).

Terms

a(0) =0a(1) =0a(2) =0a(3) =4a(4) =24a(5) =144a(6) =744a(7) =3844a(8) =19344a(9) =97344a(10) =487344a(11) =2439844a(12) =12202344a(13) =61027344a(14) =305152344a(15) =1525839844a(16) =7629277344a(17) =38146777344a(18) =190734277344a(19) =953673339844