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 A209028 #10 Mar 20 2017 09:51:10 %S A209028 1,3,5,23,88,471,2517,14611,86014,519574,3177405,19681214,123050881, %T A209028 775868013,4926859869,31483531830,202298489710,1306289630067, %U A209028 8472236548514,55167003603285,360512087413974,2363623888860990,15542899182846478,102488033365084376 %N A209028 Number of n-bead necklaces labeled with numbers -4..4 allowing reversal, with sum zero and first differences in -4..4. %H A209028 Andrew Howroyd, <a href="/A209028/b209028.txt">Table of n, a(n) for n = 1..100</a> %e A209028 Some solutions for n=6: %e A209028 .-1...-1...-3...-2...-1...-2...-4...-1...-1...-3...-3...-2...-2...-2...-3...-2 %e A209028 ..0...-1...-3....0...-1....1....0...-1....0...-1...-1....0...-1....1...-1....0 %e A209028 .-1...-1...-1...-1...-1....1....2....0...-1....0....2....0...-1...-1....2....3 %e A209028 ..1....0....2....2....0...-2....0....0....1....3...-1....0....1....2....0...-1 %e A209028 ..0....1....4...-1....3....1....2....0...-1....0....3....2....2...-1....1...-1 %e A209028 ..1....2....1....2....0....1....0....2....2....1....0....0....1....1....1....1 %Y A209028 Column 4 of A209032. %K A209028 nonn %O A209028 1,2 %A A209028 _R. H. Hardin_, Mar 04 2012 %E A209028 a(17)-a(24) from _Andrew Howroyd_, Mar 19 2017