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 A208668 #10 Mar 20 2017 09:50:15 %S A208668 4,7,12,23,44,97,212,512,1260,3251,8540,23035,62780,173453,482692, %T A208668 1353077,3811364,10785235,30625196,87239999,249174236,713416601, %U A208668 2046945140,5884580074,16946835092,48883925867,141217957620,408519816611,1183291934300,3431535849813 %N A208668 Number of 2n-bead necklaces labeled with numbers 1..5 allowing reversal, with neighbors differing by exactly 1. %H A208668 Andrew Howroyd, <a href="/A208668/b208668.txt">Table of n, a(n) for n = 1..100</a> %F A208668 a(n) = (2*A208724(n) + A090993(n))/4. - _Andrew Howroyd_, Mar 19 2017 %e A208668 All solutions for n=3: %e A208668 ..3....3....1....1....1....2....2....3....1....2....2....4 %e A208668 ..4....4....2....2....2....3....3....4....2....3....3....5 %e A208668 ..5....3....1....1....3....2....4....3....3....2....4....4 %e A208668 ..4....4....2....2....2....3....5....4....4....3....3....5 %e A208668 ..5....5....3....1....3....2....4....3....3....4....4....4 %e A208668 ..4....4....2....2....2....3....3....4....2....3....3....5 %Y A208668 Column 5 of A208671. %K A208668 nonn %O A208668 1,1 %A A208668 _R. H. Hardin_, Feb 29 2012 %E A208668 a(13)-a(30) from _Andrew Howroyd_, Mar 19 2017