This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A208598 #12 Mar 18 2018 15:18:12 %S A208598 6,23,60,125,226,371,568,825,1150,1551,2036,2613,3290,4075,4976,6001, %T A208598 7158,8455,9900,11501,13266,15203,17320,19625,22126,24831,27748,30885, %U A208598 34250,37851,41696,45793,50150,54775,59676,64861,70338,76115,82200,88601 %N A208598 Number of 4-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero. %C A208598 Row 4 of A208597. %H A208598 R. H. Hardin, <a href="/A208598/b208598.txt">Table of n, a(n) for n = 1..210</a> %F A208598 Empirical: a(n) = (4/3)*n^3 + 2*n^2 + (5/3)*n + 1. %F A208598 Conjectures from _Colin Barker_, Mar 07 2018: (Start) %F A208598 G.f.: x*(6 - x + 4*x^2 - x^3) / (1 - x)^4. %F A208598 a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4. %F A208598 (End) %e A208598 Some solutions for n=4: %e A208598 -3 -4 -3 -3 -4 -2 -2 -3 -4 -2 -3 -1 -4 -3 -4 -4 %e A208598 1 -2 4 3 0 0 0 -1 1 -2 4 -1 2 -1 1 -1 %e A208598 4 2 0 -3 3 -2 0 3 1 4 -1 2 -2 4 0 3 %e A208598 -2 4 -1 3 1 4 2 1 2 0 0 0 4 0 3 2 %Y A208598 Cf. A208597. %K A208598 nonn %O A208598 1,1 %A A208598 _R. H. Hardin_, Feb 29 2012