Number of convex polygons of length 2n on honeycomb, or EG-convex polyominoes.

Terms

a(0) =1a(1) =0a(2) =3a(3) =2a(4) =10a(5) =14a(6) =40a(7) =74a(8) =176a(9) =358a(10) =798a(11) =1670a(12) =3626a(13) =7638a(14) =16366a(15) =34462a(16) =73230a(17) =153830a(18) =324896a(19) =680514a(20) =1430336a(21) =2987310a(22) =6253712a(23) =13025954a(24) =27176052a(25) =56465878a(26) =117458820a(27) =243507250a(28) =505239264a(29) =1045301486