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A086976 Number of monotonic matrices of order n. 1
2, 19, 712, 87685, 31102080, 28757840751 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A monotonic matrix of order n is an n × N matrix in which every element is either 0 or contains a number from the set {1, 2, ..., n} subject to 3 conditions:

the filled-in entries in each row are strictly increasing;

the filled-in entries in each column are strictly decreasing;

for two filled-in cells with same entry, the one further right is higher (the positive slope condition).

See A070214 for more information.

LINKS

Table of n, a(n) for n=1..6.

Eric Weisstein's World of Mathematics, Monotonic Matrix

CROSSREFS

Cf. A070214.

Sequence in context: A290302 A278840 A300995 * A118189 A062623 A155956

Adjacent sequences:  A086973 A086974 A086975 * A086977 A086978 A086979

KEYWORD

nonn,more

AUTHOR

Eric W. Weisstein, Jul 25 2003

EXTENSIONS

a(4) from Rob Pratt, Aug 23 2003

a(5)-a(6) from Giovanni Resta, Jul 28 2015

STATUS

approved

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Last modified August 10 08:28 EDT 2020. Contains 336368 sequences. (Running on oeis4.)