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%I #8 Jul 21 2018 10:06:01
%S 28,99,350,1238,4379,15490,54793,193821,685609,2425226,8578828,
%T 30346157,107344412,379712753,1343169821,4751236703,16806698494,
%U 59450861306,210297394895,743891565706,2631390949017,9308101672049,32925839761497
%N Half the number of 0..3 arrays of length n+2 with second differences nonzero.
%C Column 3 of A212782.
%H R. H. Hardin, <a href="/A212777/b212777.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 2*a(n-1) + 5*a(n-2) + 3*a(n-3) - 4*a(n-4) - 4*a(n-5).
%F Empirical g.f.: x*(28 + 43*x + 12*x^2 - 41*x^3 - 32*x^4) / (1 - 2*x - 5*x^2 - 3*x^3 + 4*x^4 + 4*x^5). - _Colin Barker_, Jul 21 2018
%e Some solutions for n=5:
%e ..3....0....3....3....3....3....2....2....3....3....1....3....1....3....0....0
%e ..1....3....1....2....3....3....2....2....2....3....0....1....0....1....1....1
%e ..3....0....0....3....1....1....0....0....3....0....1....3....2....1....3....0
%e ..1....0....1....0....2....0....3....1....3....3....3....2....2....3....1....3
%e ..1....3....0....1....2....0....0....3....2....3....2....3....1....3....0....3
%e ..2....3....1....0....0....1....2....2....2....0....0....0....2....0....0....1
%e ..1....1....1....1....1....0....3....2....0....1....3....2....2....3....1....3
%Y Cf. A212782.
%K nonn
%O 1,1
%A _R. H. Hardin_, May 27 2012