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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A221625 Number of 3Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row.

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%I A221625 #6 Jul 23 2025 02:04:00
%S A221625 1,4,112,6120,738150,148700748,49096652080,24099422236160,
%T A221625 17023170538890750,16517958827528755300,21433818529290626472948,
%U A221625 36180795747764068402865136,77856103174007703918070147632
%N A221625 Number of 3Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row.
%C A221625 Row 3 of A221623
%H A221625 R. H. Hardin, <a href="/A221625/b221625.txt">Table of n, a(n) for n = 1..14</a>
%e A221625 Some solutions for n=3
%e A221625 ..3..1..2....1..2..3....1..3..2....1..2..3....1..2..3....2..3..1....2..3..1
%e A221625 ..1..3..2....3..1..2....3..1..2....1..2..3....2..1..3....2..3..1....1..3..2
%e A221625 ..1..3..2....2..3..1....3..2..1....1..2..3....3..2..1....2..1..3....3..1..2
%K A221625 nonn
%O A221625 1,2
%A A221625 _R. H. Hardin_ Jan 21 2013

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