A162109 Number of n X n symmetric binary arrays with rows, considered as graycode numbers, in strictly increasing order.
2, 4, 9, 56, 499, 8000, 207554, 9382078, 732814910, 101599273769, 25151730678684, 11252735518379960, 9169484084583765409, 13716523699765295956974, 37907229783585348802398136, 194640906178869631364050052914
Offset: 1