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 A209342 #6 Mar 12 2017 23:36:38 %S A209342 1,7,24,205,1724,16968,172610,1830872,19860306,219630346,2464760150, %T A209342 28002352120 %N A209342 Number of n-bead necklaces labeled with numbers -6..6 allowing reversal, with sum zero with no three beads in a row equal. %C A209342 Column 6 of A209344. %e A209342 Some solutions for n=6: %e A209342 .-5...-5...-5...-3...-6...-4...-6...-6...-6...-4...-4...-5...-5...-6...-5...-6 %e A209342 ..0...-2....3....3....3...-2...-6....5....3...-3...-1...-2...-5...-1...-4....4 %e A209342 ..2....1...-4...-3...-5....6....2...-6....5....1....1...-2....3....4....6...-5 %e A209342 .-3...-2....4....3....2...-4....3....5...-5....3....4....5....2....4....6....6 %e A209342 ..2....3...-2...-3....3....3....2...-3...-1....0....0....2....0...-3...-5...-5 %e A209342 ..4....5....4....3....3....1....5....5....4....3....0....2....5....2....2....6 %K A209342 nonn %O A209342 1,2 %A A209342 _R. H. Hardin_, Mar 06 2012