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A202118 Number of -2..2 arrays of n elements with first, second and third differences also in -2..2.

%I A202118 #7 Jun 02 2025 07:23:48
%S A202118 5,19,57,127,293,663,1517,3459,7905,18051,41239,94203,215217,491661,
%T A202118 1123219,2566023,5862189,13392389,30595439,69896451,159681185,
%U A202118 364797903,833395099,1903923685,4349588175,9936804401,22701018621,51861365563
%N A202118 Number of -2..2 arrays of n elements with first, second and third differences also in -2..2.
%C A202118 Column 2 of A202124
%H A202118 R. H. Hardin, <a href="/A202118/b202118.txt">Table of n, a(n) for n = 1..210</a>
%F A202118 Empirical: a(n) = 2*a(n-1) +a(n-3) +3*a(n-4) -2*a(n-5) -3*a(n-6) -4*a(n-7) -3*a(n-8) -2*a(n-9) +3*a(n-10) +4*a(n-11) +2*a(n-12) for n>17
%e A202118 Some solutions for n=7
%e A202118 ..1...-1...-1....1....1....1...-2....1....0....2...-2...-2....0....1....1....0
%e A202118 ..0...-2...-2....1...-1....1....0....1....2....2....0...-2...-1....0....1...-1
%e A202118 ..0...-2...-2....2...-1....0....0....2....2....1....2...-1...-1....0....0...-2
%e A202118 .-1...-2...-1....2...-1....0....0....2....2....1....2....0...-1....1....0...-1
%e A202118 .-1....0....1....2...-1...-1....1....2....1....0....1....1....0....1....0....0
%e A202118 .-1....2....2....1...-1...-2....2....0...-1...-1....1....1....0....1....0....0
%e A202118 ..1....2....1....1...-1...-2....2...-2...-2....0....2....0....1....2...-1...-1
%K A202118 nonn
%O A202118 1,1
%A A202118 _R. H. Hardin_ Dec 11 2011