Number of staircase polygons of area n with 2 (staircase polygon) holes on square lattice (not allowing rotations).

A057415

Number of staircase polygons of area n with 2 (staircase polygon) holes on square lattice (not allowing rotations).

Terms

    a(0) =2a(1) =10a(2) =53a(3) =220a(4) =845a(5) =2975a(6) =9936a(7) =31640a(8) =97283a(9) =290173a(10) =844729a(11) =2408213a(12) =6746197a(13) =18613290a(14) =50688554a(15) =136464665a(16) =363724034a(17) =960862781a(18) =2518380075a(19) =6554072749a(20) =16949040877a(21) =43580221577a(22) =111475092069a(23) =283799832989

External references