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 A309673 #17 Oct 10 2019 20:33:47
%S A309673 0,1,1,3,2,9,13,41,94,257,671,1881,5110,14301,39871,112281,316520,
%T A309673 897297,2548819,7265383,20754748,59437181,170549237,490338539,
%U A309673 1412147684,4073528481,11767897903,34042917197,98606864030,285960106473,830206177801,2412787265021
%N A309673 Number of n-bead necklace structures using a maximum of four different colored beads and no adjacent beads having the same color.
%C A309673 Colors may be permuted without changing the necklace structure.
%H A309673 Andrew Howroyd, <a href="/A309673/b309673.txt">Table of n, a(n) for n = 1..200</a>
%F A309673 a(n) = Sum_{k=1..4} A327396(n, k).
%Y A309673 Cf. A056292, A306888, A327396, A328130.
%K A309673 nonn
%O A309673 1,4
%A A309673 _Andrew Howroyd_, Oct 05 2019
%E A309673 Terms a(24) and beyond from _Andrew Howroyd_, Oct 10 2019