21477012

Appears in sequences

• Number of polyiamonds with n cells that tile the plane by 180-degree rotation (Conway criterion) but not by translation.at n=28A075219
• Number of polyiamonds with n cells that tile the plane by 180-degree rotation (Conway criterion).at n=28A075220
• Number of polyiamonds with n cells that tile the plane by translation or by 180-degree rotation (Conway criterion).at n=28A075221