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 A257846 #17 Jun 13 2015 00:55:37
%S A257846 0,0,0,0,0,0,0,1,2,3,4,5,0,2,4,6,8,10,0,3,6,9,12,15,0,4,8,12,16,20,0,
%T A257846 5,10,15,20,25,0,6,12,18,24,30,0,7,14,21,28,35,0,8,16,24,32,40,0,9,18,
%U A257846 27,36,45,0,10,20,30,40,50,0,11,22,33,44,55,0,12,24
%N A257846 a(n) = floor(n/6) * (n mod 6).
%C A257846 Equivalently, write n in base 6, multiply the last digit by the number with its last digit removed.
%H A257846 Colin Barker, <a href="/A257846/b257846.txt">Table of n, a(n) for n = 0..1000</a>
%H A257846 <a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,2,0,0,0,0,0,-1).
%F A257846 a(n) = 2*a(n-6)-a(n-12). - _Colin Barker_, May 11 2015
%F A257846 G.f.: x^7*(5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x+1)^2*(x^2-x+1)^2*(x^2+x+1)^2). - _Colin Barker_, May 11 2015
%t A257846 Table[Floor[n/6]*Mod[n, 6], {n, 120}] (* _Michael De Vlieger_, May 11 2015 *)
%o A257846 (PARI) a(n,b=6)=(n=divrem(n,b))[1]*n[2]
%o A257846 (PARI) concat([0, 0, 0, 0, 0, 0, 0], Vec(x^7*(5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x+1)^2*(x^2-x+1)^2*(x^2+x+1)^2) + O(x^100))) \\ _Colin Barker_, May 11 2015
%Y A257846 Cf. A142150 (the base 2 analog), A115273, A257844 - A257850.
%K A257846 nonn,easy
%O A257846 0,9
%A A257846 _M. F. Hasler_, May 10 2015