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 A241217 #26 Aug 01 2024 01:19:10
%S A241217 1,14,142,1428,14285,142857,1428571,14285714,142857142,1428571428,
%T A241217 14285714285,142857142857,1428571428571,14285714285714,
%U A241217 142857142857142,1428571428571428,14285714285714285,142857142857142857,1428571428571428571,14285714285714285714
%N A241217 Largest number that when multiplied by 7 produces an n-digit number.
%C A241217 The definition "largest number that when multiplied by 3 produces an n-digit number" gives A002277.
%D A241217 Albert H. Beiler, Recreations in the theory of numbers, New York, Dover, (2nd ed.) 1966. See Table 34 at p. 62.
%H A241217 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10,-1,11,-10).
%F A241217 a(n) = floor(10^n/7). - _Michel Marcus_, Apr 21 2014
%F A241217 G.f.: x*(1+3*x-2*x^2+7*x^3)/((x-1)*(10*x-1)*(x+1)*(x^2-x+1)). - _Alois P. Heinz_, Apr 30 2014
%F A241217 E.g.f.: (3*cosh(10*x) - 7*cosh(x) + 2*exp(x/2)*(2*cos(sqrt(3)*x/2) + sqrt(3)*sin(sqrt(3)*x/2)) - 14*sinh(x) + 3*sinh(10*x))/21. - _Stefano Spezia_, Jul 31 2024
%e A241217 14*7 = 98 but 15*7 = 105 (too large) so a(2) = 14.
%t A241217 LinearRecurrence[{11,-10,-1,11,-10},{1,14,142,1428,14285},30] (* _Harvey P. Dale_, Mar 03 2024 *)
%o A241217 (PARI) a(n) = floor(10^n/7); \\ _Michel Marcus_, Apr 21 2014
%Y A241217 Cf. A020806, A002277.
%K A241217 nonn,base,easy
%O A241217 1,2
%A A241217 _J. Lowell_, Apr 17 2014
%E A241217 More terms from _Michel Marcus_, Apr 21 2014