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%I #6 May 11 2023 11:03:34
%S 3,9,16,50,138,387,1143,3402,9948,30747,90018,266959,805676,2433677,
%T 7192342,21660095,64921118,194318785,583516248,1749692999,5235795129,
%U 15779920510,47191559739,141322913448,424521847845,1275708336588
%N Number of n X 1 0..2 arrays with all rows and columns having a nonnegative second derivative in a quadratic least squares fit, with one and two element arrays taken as having a zero second derivative.
%C Column 1 of A223195.
%H R. H. Hardin, <a href="/A223188/b223188.txt">Table of n, a(n) for n = 1..83</a>
%e All solutions for n=3
%e ..1....1....2....0....2....1....2....0....2....2....0....1....2....0....2....1
%e ..1....0....0....0....0....0....2....0....1....0....1....0....1....0....1....1
%e ..2....1....2....1....1....0....2....2....0....0....2....2....1....0....2....1
%Y Cf. A223195.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 18 2013