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 A208715 #12 Mar 12 2017 22:51:21 %S A208715 1,3,7,18,38,100,224,600,1498,4124,11054,31347,87887,253251,727867, %T A208715 2117551,6159994,18022052,52757222,154874172,454989753,1338737083, %U A208715 3941860229,11618101775,34264747423,101127761931,298632667837,882370316215,2608423280534,7714578529582 %N A208715 Number of n-bead necklaces labeled with numbers 1..n allowing reversal, with no adjacent beads differing by more than 1. %H A208715 Andrew Howroyd, <a href="/A208715/b208715.txt">Table of n, a(n) for n = 1..100</a> %e A208715 All solutions for n=3: %e A208715 ..2....2....1....3....2....1....1 %e A208715 ..2....2....1....3....3....2....1 %e A208715 ..2....3....2....3....3....2....1 %Y A208715 Diagonal of A208721. %K A208715 nonn %O A208715 1,2 %A A208715 _R. H. Hardin_, Mar 01 2012 %E A208715 a(17)-a(30) from _Andrew Howroyd_, Mar 03 2017