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 A272000 #21 Apr 29 2020 21:24:53
%S A272000 3,11,29,47,79,111,161,211,283,355,453,551,679,807,969,1131,1331,1531,
%T A272000 1773,2015,2303,2591,2929,3267,3659,4051,4501,4951,5463,5975,6553,
%U A272000 7131,7779,8427,9149,9871,10671,11471,12353,13235,14203,15171,16229,17287,18439
%N A272000 Coinage sequence: a(n) = A018227(n)-7.
%C A272000 Terms from 29 to 111 are the atomic numbers of the elements of group 11 in the periodic table. The group is also known as the coinage metals since copper (element 29), silver (element 47) and gold (element 79) are in group 11.
%H A272000 Colin Barker, <a href="/A272000/b272000.txt">Table of n, a(n) for n = 1..1000</a>
%H A272000 Wikipedia, <a href="https://en.wikipedia.org/wiki/Group_11_element">Group 11 element</a>.
%H A272000 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2,1,-4,1,2,-1).
%F A272000 From _Colin Barker_, Oct 25 2016: (Start)
%F A272000 G.f.: x*(3 + 5*x + 4*x^2 - 10*x^3 - 3*x^4 + 5*x^5)/((1 - x)^4*(1 + x)^2).
%F A272000 a(n) = 2*a(n-1) + a(n-2) - 4*a(n-3) + a(n-4) + 2*a(n-5) - a(n-6) for n>6.
%F A272000 a(n) = (n^3 + 9*n^2 + 26*n - 30)/6 for n even.
%F A272000 a(n) = (n^3 + 9*n^2 + 29*n - 21)/6 for n odd. (End)
%t A272000 LinearRecurrence[{2,1,-4,1,2,-1},{3,11,29,47,79,111},50] (* _Harvey P. Dale_, Nov 26 2018 *)
%o A272000 (PARI) Vec(x*(3+5*x+4*x^2-10*x^3-3*x^4+5*x^5)/((1-x)^4*(1+x)^2) + O(x^60)) \\ _Colin Barker_, Oct 25 2016
%Y A272000 Other groups: 1(A219527), 2(A168380), 3(A168388), 12(A271998), 13(A271997), 14(A271996), 15(A271995), 16(A271994), 17(A271999), 18(A018227).
%K A272000 nonn,easy
%O A272000 1,1
%A A272000 _Natan Arie Consigli_, Jul 02 2016