A145793 - OEIS

A145793

Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only either four adjacent vertically or four adjacent horizontally.

1, 1, 1, 1, 1, 2, 3, 5, 8, 17, 40, 108, 294, 944, 3040, 12114, 49757, 243775, 1210271, 7153531, 43484383, 316861269, 2366046579, 21108349931, 192219307524, 2092034177623, 23326966046445, 311290850669433, 4251413939111348