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 A209024 #11 Mar 20 2017 09:51:02 %S A209024 1,2,4,23,187,2798,52208,1210780,32915700,1029158718,36366029268, %T A209024 1434017630862,62448855324545,2977529703278272,154305670613042906, %U A209024 8637641797383212010,519466811614545786362,33406493488132547194879,2287819864082225737308655,166242770253180661727941435 %N A209024 Number of n-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero and first differences in -n..n. %e A209024 Some solutions for n=6: %e A209024 .-4...-6...-4...-3...-3...-2...-5...-4...-5...-3...-3...-5...-4...-6...-3...-4 %e A209024 ..0...-2...-2...-1...-2....0...-1....0...-3...-1...-2...-5...-3....0...-2....0 %e A209024 .-2....3....3....1....3....1....2...-1....2...-1....4....0....0....0...-1....2 %e A209024 ..4....3....4....3...-1...-2....3....5....0....1...-1....6....3....0....0....3 %e A209024 ..0....4...-1....0....1....1....2....0....5....4....2....3....4....6....4...-2 %e A209024 ..2...-2....0....0....2....2...-1....0....1....0....0....1....0....0....2....1 %Y A209024 Diagonal of A209032. %K A209024 nonn %O A209024 1,2 %A A209024 _R. H. Hardin_, Mar 04 2012 %E A209024 a(12)-a(20) from _Andrew Howroyd_, Mar 19 2017