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A219286 Number of n X 3 arrays of the minimum value of corresponding elements and their horizontal or vertical neighbors in a random, but sorted with lexicographically nondecreasing rows and columns, 0..1 n X 3 array. 1

%I

%S 3,6,19,42,79,136,220,339,502,719,1001,1360,1809,2362,3034,3841,4800,

%T 5929,7247,8774,10531,12540,14824,17407,20314,23571,27205,31244,35717,

%U 40654,46086,52045,58564,65677,73419,81826,90935,100784,111412,122859

%N Number of n X 3 arrays of the minimum value of corresponding elements and their horizontal or vertical neighbors in a random, but sorted with lexicographically nondecreasing rows and columns, 0..1 n X 3 array.

%C Column 3 of A219291.

%H R. H. Hardin, <a href="/A219286/b219286.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = (1/24)*n^4 + (1/4)*n^3 - (1/24)*n^2 + (27/4)*n - 11 for n>2.

%F Conjectures from _Colin Barker_, Jul 25 2018: (Start)

%F G.f.: x*(3 - 9*x + 19*x^2 - 23*x^3 + 14*x^4 - 2*x^5 - x^6) / (1 - x)^5.

%F a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>7.

%F (End)

%e Some solutions for n=3:

%e ..0..0..1....0..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0

%e ..0..0..1....0..0..1....0..0..0....0..0..0....0..0..1....0..0..0....0..0..1

%e ..0..1..1....0..0..0....1..0..0....0..1..0....1..1..1....0..0..1....0..0..1

%Y Cf. A219291.

%K nonn

%O 1,1

%A _R. H. Hardin_, Nov 17 2012

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Last modified January 27 03:09 EST 2022. Contains 350601 sequences. (Running on oeis4.)