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A086976
Number of monotonic matrices of order n.
1
2, 19, 712, 87685, 31102080, 28757840751
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
Eric Weisstein's World of Mathematics, Monotonic Matrix
CROSSREFS
Cf. A070214.
Sequence in context: A290302 A278840 A300995 * A118189 A062623 A155956
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