A162057 - OEIS

A162057

Number of n X n symmetric binary arrays with rows, considered as graycode numbers, in nondecreasing order, and no more than 2 ones in any row or column

2, 6, 13, 34, 86, 233, 652, 1888, 5683, 17526, 55868, 182024, 609103, 2081152, 7268823, 25891230, 93983793, 347398900, 1306005890, 4991876362, 19377811110, 76372139937, 305348766558, 1238006401576, 5086973436072