Number of polyhexes with n cells that tile the plane isohedrally.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =22a(5) =76a(6) =290a(7) =1018a(8) =3715a(9) =11068a(10) =24289a(11) =102642a(12) =163176a(13) =527675a(14) =1569567a(15) =2929322a(16) =4752512a(17) =21006062a(18) =24293375a(19) =95578494a(20) =205091895