For every cell of a polyomino let c be the number of cells that are in the same row or in the same column (including itself). a(n) is the sum of the c values of all cells of all free polyominoes with n cells.

A365860

For every cell of a polyomino let c be the number of cells that are in the same row or in the same column (including itself). a(n) is the sum of the c values of all cells of all free polyominoes with n cells.