A181344 Number of n X n matrices over {0,1} with rows and columns summing to 3, rows and columns sorted (>=) by value.

0, 0, 1, 1, 5, 25, 161, 1112, 8787, 76156, 728699, 7609065, 86162795, 1050755884, 13728407061, 191309852944

Offset

1,5

Links

Table of n, a(n) for n=1..16.

Bert Dobbelaere, Illustration of initial terms.

Krasimir Yordzhev, On some classes of binary matrices, Notes Num. Theor. Disc. Math. 31(4) (2025) 728-735. See p. 730.

Example

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

Crossrefs

Cf. A000512, A001501, A181345.

Sequence in context: A137963 A366435 A144887 * A361916 A356596 A134007

Adjacent sequences: A181341 A181342 A181343 * A181345 A181346 A181347

Keyword

hard,more,nonn

Author

Michael Steyer (m.steyer(AT)osram.de), Oct 14 2010

Extensions

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

Status

approved