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 A060560 #26 Dec 26 2024 15:20:39
%S A060560 0,1,30,498,4435,25395,107331,365260,1058058,2707245,6278140,13442286,
%T A060560 26942565,51084943,92383305,160386360,268718116,436365945,689252778,
%U A060560 1062132490,1600850055,2365010571,3431103775,4896133188,6881801550,9539306725,13054804776,17655599430
%N A060560 Number of ways to color the vertices of an octagon using <= n colors, allowing rotations and reflections.
%C A060560 In Williamson's terminology, this is "Number of 8-hoops with n symbols."
%H A060560 Harry J. Smith, <a href="/A060560/b060560.txt">Table of n, a(n) for n=0..500</a>
%H A060560 S. G. Williamson, <a href="http://dx.doi.org/10.1016/0012-365X(72)90043-X">The combinatorial analysis of patterns and the principle of inclusion-exclusion</a>, Discrete Math. 1 (1972), no. 4, 357--388. MR0299493 (45 #8541). - _N. J. A. Sloane_, Mar 27 2012
%H A060560 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (9,-36,84,-126,126,-84,36,-9,1).
%F A060560 a(n) = n*(n + 1)*(n^6 - n^5 + n^4 + 3*n^3 + 2*n^2 - 2*n + 4)/16.
%F A060560 G.f.: x*(1 + 21*x + 264*x^2 + 949*x^3 + 1014*x^4 + 258*x^5 + 13*x^6)/(1 - x)^9. - _Colin Barker_, Jan 29 2012
%o A060560 (PARI) a(n) = { (n^8 + 4*n^5 + 5*n^4 + 2*n^2 + 4*n)/16 } \\ _Harry J. Smith_, Jul 07 2009
%Y A060560 Cf. A081720, A210766, A210768, A295925.
%K A060560 nonn
%O A060560 0,3
%A A060560 _N. J. A. Sloane_, Apr 12 2001