Number of ways to place two non-attacking rooks on all free n-ominoes.
A171011
Number of ways to place two non-attacking rooks on all free n-ominoes.
Terms
- a(0) =0a(1) =0a(2) =1a(3) =9a(4) =48a(5) =242a(6) =1178a(7) =5793a(8) =27651a(9) =131383
External references
- oeis: A171011