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Number of 3 X n 0..1 arrays with antidiagonals unimodal and rows and diagonals nondecreasing.
1

%I #8 Aug 26 2018 11:11:16

%S 8,21,37,58,85,119,161,212,273,345,429,526,637,763,905,1064,1241,1437,

%T 1653,1890,2149,2431,2737,3068,3425,3809,4221,4662,5133,5635,6169,

%U 6736,7337,7973,8645,9354,10101,10887,11713,12580,13489,14441,15437,16478

%N Number of 3 X n 0..1 arrays with antidiagonals unimodal and rows and diagonals nondecreasing.

%C Row 3 of A224038.

%H R. H. Hardin, <a href="/A224039/b224039.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = (1/6)*n^3 + 1*n^2 + (47/6)*n for n>1.

%F Conjectures from _Colin Barker_, Aug 26 2018: (Start)

%F G.f.: x*(8 - 11*x + x^2 + 4*x^3 - x^4) / (1 - x)^4.

%F a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>5.

%F (End)

%e Some solutions for n=3:

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

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

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

%Y Cf. A224038.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 30 2013