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 A093367 #16 Nov 12 2024 19:51:58
%S A093367 0,0,2,3,6,11,18,33,58,105,186,349,630,1179,2190,4113,7710,14599,
%T A093367 27594,52485,99878,190743,364722,699249,1342182,2581425,4971066,
%U A093367 9587577,18512790,35792565,69273666,134219793,260301174,505294125,981706830,1908881897,3714566310
%N A093367 Number of n-bead necklaces using exactly three colors with no adjacent beads having the same color.
%C A093367 Original name: number of periodic cycles of iterative map described by Ma and Wainwright.
%D A093367 David W. Hobill and Scott MacDonald (zeened(AT)shaw.ca), Preprint, 2004.
%D A093367 P. K.-H. Ma and J. Wainwright, A dynamical systems approach to the oscillatory singularity in Bianchi cosmologies, Relativity Today, 1994.
%H A093367 P. K.-H. Ma and J. Wainwright, <a href="https://doi.org/10.1007/978-1-4757-9993-4_25">A dynamical systems approach to the oscillatory singularity in Bianchi cosmologies</a>, Deterministic Chaos in General Relativity, pp. 449-462, 1994.
%F A093367 a(n) = A000031(n) - (5 + (-1)^n)/2. - _Andrew Howroyd_, Dec 21 2019
%e A093367 a(3) = 2 because the two necklaces 123 and 132 have no adjacent equal elements. - _Andrew Howroyd_, Dec 21 2019
%t A093367 Table[Mod[n, 2] - 3 + DivisorSum[n, EulerPhi[n/#] 2^# &]/n, {n, 37}] (* _Michael De Vlieger_, Dec 22 2019 *)
%o A093367 (PARI) a(n)={n%2 - 3 + sumdiv(n, d, eulerphi(n/d)*2^d)/n} \\ _Andrew Howroyd_, Dec 21 2019
%Y A093367 Column 3 of A330618.
%Y A093367 Cf. A000031, A093368.
%K A093367 nonn
%O A093367 1,3
%A A093367 _N. J. A. Sloane_, Apr 28 2004
%E A093367 Name changed by _Andrew Howroyd_, Dec 21 2019
%E A093367 a(1)-a(2) prepended and terms a(20) and beyond from _Andrew Howroyd_, Dec 21 2019