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%I #8 Aug 26 2018 09:50:56
%S 20,400,6796,112436,1859020,30756756,508916456,8420768936,
%T 139333478144,2305467501680,38147189410288,631198698504112,
%U 10444066884547776,172811720487440320,2859412053301829248,47312978931444876928
%N Number of n X 3 0..3 arrays with rows nondecreasing and antidiagonals unimodal.
%C Column 3 of A224024.
%H R. H. Hardin, <a href="/A224019/b224019.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 20*a(n-1) - 70*a(n-2) + 228*a(n-3) - 276*a(n-4) + 392*a(n-5) - 196*a(n-6) + 144*a(n-7).
%F Empirical g.f.: 4*x*(5 + 49*x^2 - 11*x^3 + 85*x^4 - 13*x^5 + 36*x^6) / (1 - 20*x + 70*x^2 - 228*x^3 + 276*x^4 - 392*x^5 + 196*x^6 - 144*x^7). - _Colin Barker_, Aug 26 2018
%e Some solutions for n=3:
%e ..1..1..1....0..0..0....2..3..3....1..1..3....0..0..0....0..1..3....0..0..0
%e ..2..3..3....2..3..3....0..2..2....0..3..3....1..1..1....0..1..1....2..2..2
%e ..2..2..2....2..3..3....0..1..1....1..2..2....1..3..3....1..1..1....2..2..3
%Y Cf. A224024.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 30 2013
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