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%I #11 Oct 03 2025 09:38:26
%S 1,3,5,15,21,53,109,239,489,1051,2253,4853,10511,23033,50791,112187,
%T 248217,549917,1220585,2712351,6037825,13459637,30045375,67137267,
%U 150165265,336151499,753099801,1688448381,3788174371,8504582261
%N Number of zero-sum -2..2 arrays of n elements with first through third differences also in -2..2.
%C Column 2 of A202511
%H R. H. Hardin, <a href="/A202505/b202505.txt">Table of n, a(n) for n = 1..210</a>
%e Some solutions for n=7
%e ..0...-1....1....2....0...-1...-2...-1...-2....0....2....2....2....1...-2....0
%e ..1....0....0....0...-1...-2...-2....0...-1...-1....0....0....1....1...-2....0
%e ..2....1....0...-2...-1...-1...-2....1...-1....0...-1...-1....1....0....0....0
%e ..1....1....0...-2....0....0....0....2....0....1...-1....0....0....0....2....0
%e .-1....1...-1...-1....0....1....2....1....1....1....0....1...-1....0....2....0
%e .-2....0...-1....1....1....1....2...-1....2....0....0....0...-1....0....1....0
%e .-1...-2....1....2....1....2....2...-2....1...-1....0...-2...-2...-2...-1....0
%K nonn
%O 1,2
%A _R. H. Hardin_, Dec 20 2011