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 A208721 #7 Mar 13 2017 00:28:55 %S A208721 1,2,1,3,3,1,4,5,4,1,5,7,7,6,1,6,9,10,12,8,1,7,11,13,18,18,13,1,8,13, %T A208721 16,24,28,34,18,1,9,15,19,30,38,56,56,30,1,10,17,22,36,48,78,98,111, %U A208721 46,1,11,19,25,42,58,100,140,208,207,78,1,12,21,28,48,68,122,182,306,418,427,126 %N A208721 T(n,k) = number of n-bead necklaces labeled with numbers 1..k allowing reversal, with no adjacent beads differing by more than 1. %C A208721 Table starts %C A208721 .1..2...3...4...5...6...7...8...9..10..11..12...13...14...15...16...17...18 %C A208721 .1..3...5...7...9..11..13..15..17..19..21..23...25...27...29...31...33...35 %C A208721 .1..4...7..10..13..16..19..22..25..28..31..34...37...40...43...46...49...52 %C A208721 .1..6..12..18..24..30..36..42..48..54..60..66...72...78...84...90...96..102 %C A208721 .1..8..18..28..38..48..58..68..78..88..98.108..118..128..138..148..158..168 %C A208721 .1.13..34..56..78.100.122.144.166.188.210.232..254..276..298..320..342..364 %C A208721 .1.18..56..98.140.182.224.266.308.350.392.434..476..518..560..602..644..686 %C A208721 .1.30.111.208.306.404.502.600.698.796.894.992.1090.1188.1286.1384.1482.1580 %H A208721 R. H. Hardin, <a href="/A208721/b208721.txt">Table of n, a(n) for n = 1..397</a> %e A208721 All solutions for n=4, k=3: %e A208721 ..2....3....2....2....1....2....1....2....1....1....1....1 %e A208721 ..3....3....2....3....1....2....1....2....2....2....1....2 %e A208721 ..2....3....3....3....2....2....1....2....1....3....1....2 %e A208721 ..3....3....3....3....2....2....1....3....2....2....2....2 %Y A208721 Column 2 is A000029. %K A208721 nonn,tabl %O A208721 1,2 %A A208721 _R. H. Hardin_, Mar 01 2012