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 A257847 #15 Nov 12 2022 18:00:27
%S A257847 0,0,0,0,0,0,0,0,1,2,3,4,5,6,0,2,4,6,8,10,12,0,3,6,9,12,15,18,0,4,8,
%T A257847 12,16,20,24,0,5,10,15,20,25,30,0,6,12,18,24,30,36,0,7,14,21,28,35,42,
%U A257847 0,8,16,24,32,40,48,0,9,18,27,36,45,54,0,10,20
%N A257847 a(n) = floor(n/7) * (n mod 7).
%C A257847 Equivalently, write n in base 7, multiply the last digit by the number with its last digit removed.
%H A257847 Colin Barker, <a href="/A257847/b257847.txt">Table of n, a(n) for n = 0..1000</a>
%H A257847 <a href="/index/Rec#order_14">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,2,0,0,0,0,0,0,-1).
%F A257847 a(n) = 2*a(n-7)-a(n-14). - _Colin Barker_, May 11 2015
%F A257847 G.f.: x^8*(6*x^5+5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x^6+x^5+x^4+x^3+x^2+x+1)^2). - _Colin Barker_, May 11 2015
%t A257847 Table[Floor[n/7]Mod[n,7],{n,0,80}] (* _Harvey P. Dale_, Nov 12 2022 *)
%o A257847 (PARI) a(n,b=7)=(n=divrem(n,b))[1]*n[2]
%o A257847 (PARI) concat([0,0,0,0,0,0,0,0], Vec(x^8*(6*x^5+5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x^6+x^5+x^4+x^3+x^2+x+1)^2) + O(x^100))) \\ _Colin Barker_, May 11 2015
%Y A257847 Cf. A194757.
%Y A257847 Cf. A142150 (the base 2 analog), A115273, A257844 - A257850.
%K A257847 nonn,base,easy
%O A257847 0,10
%A A257847 _M. F. Hasler_, May 10 2015