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

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =12a(6) =23a(7) =66a(8) =133a(9) =316a(10) =514a(11) =1987a(12) =2398a(13) =6073a(14) =12628a(15) =29918a(16) =26211a(17) =108778a(18) =95348a(19) =375045a(20) =498168a(21) =780434a(22) =843319a(23) =4981628a(24) =3691212a(25) =7357764a(26) =13169722a(27) =33461765a(28) =22372303a(29) =117437124