A181345 Number of n X n matrices over {0,1} with rows and columns summing to 3, rows and columns sorted (>) by value.

0, 0, 0, 1, 2, 12, 87, 662, 5611, 51141, 509277, 5504398, 64122940, 800741192, 10673478573, 151323048909

Offset: 1

Author

Michael Steyer (m.steyer(AT)osram.de), Oct 18 2010

Keywords

• hard
• nonn

Examples

			n=4: {1110,1101,1011,0111} is the only matrix where each row (column) - read as a binary number - is larger than the previous one, so a(4)=1.
		

Links

• Bert Dobbelaere, Illustration of initial terms

Crossrefs

Cf. A000512, A001501, A181344.

Extensions

Offset corrected and a(10)-a(16) from Bert Dobbelaere, Feb 23 2020