Half the number of n X n symmetric binary matrices with every 1 adjacent to some 0 horizontally or vertically and every 0 adjacent to some 1 horizontally or vertically.
A140422
Half the number of n X n symmetric binary matrices with every 1 adjacent to some 0 horizontally or vertically and every 0 adjacent to some 1 horizontally or vertically.
Terms
- a(0) =1a(1) =5a(2) =47a(3) =849a(4) =29241a(5) =1901849a(6) =234932757a(7) =55047807551
External references
- oeis: A140422