A181344 - OEIS

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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

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OFFSET

1,5

LINKS

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

Bert Dobbelaere, Illustration of initial terms

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