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A202077 Number of arrays of 5 integers in -n..n with sum zero and the sum of every adjacent pair being odd. 1

%I

%S 2,26,78,264,504,1128,1786,3262,4660,7540,10092,15066,19278,27174,

%T 33644,45428,54846,71622,84770,107780,125532,156156,179478,219234,

%U 249184,299728,337456,400582,447330,524970,582072,676296,745178,858194,940374

%N Number of arrays of 5 integers in -n..n with sum zero and the sum of every adjacent pair being odd.

%C Row 3 of A202076.

%H R. H. Hardin, <a href="/A202077/b202077.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = a(n-1) + 4*a(n-2) - 4*a(n-3) - 6*a(n-4) + 6*a(n-5) + 4*a(n-6) - 4*a(n-7) - a(n-8) + a(n-9).

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

%F G.f.: 2*x*(1 + 12*x + 22*x^2 + 45*x^3 + 22*x^4 + 12*x^5 + x^6) / ((1 - x)^5*(1 + x)^4).

%F a(n) = (230*n^4 + 552*n^3 + 424*n^2 + 96*n) / 384 for n even.

%F a(n) = (230*n^4 + 368*n^3 + 148*n^2 + 16*n + 6) / 384 for n odd.

%F (End)

%e Some solutions for n=3:

%e -2 0 0 -2 0 2 0 0 2 2 -2 2 2 2 -2 2

%e -1 -1 -3 1 -1 -1 -1 3 1 -3 3 1 -3 -3 1 -3

%e 0 2 2 0 0 0 2 -2 -2 -2 2 0 0 2 -2 0

%e 1 -3 1 -1 -1 -1 1 -1 -1 3 -3 -3 -1 -1 3 3

%e 2 2 0 2 2 0 -2 0 0 0 0 0 2 0 0 -2

%Y Cf. A202076.

%K nonn

%O 1,1

%A _R. H. Hardin_, Dec 10 2011

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Last modified August 18 16:18 EDT 2022. Contains 356215 sequences. (Running on oeis4.)