Number of oriented polyominoes with 4n cells that have fourfold rotational symmetry centered at a vertex.

A348848

Number of oriented polyominoes with 4n cells that have fourfold rotational symmetry centered at a vertex.

Terms

    a(0) =1a(1) =2a(2) =6a(3) =19a(4) =65a(5) =224a(6) =790a(7) =2851a(8) =10424a(9) =38496a(10) =143454a(11) =538667a(12) =2035180a(13) =7729146a(14) =29486904a(15) =112942373a(16) =434114384a(17) =1673766428a(18) =6471199322a(19) =25081542410a(20) =97431694571a(21) =379256586232

External references