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 A254500 #41 Mar 21 2019 13:25:34
%S A254500 0,7,17,70,111,258,689,454,7133,15977,82869,111044,536687,384769,
%T A254500 2750561,7063105
%N A254500 a(n) is the smallest nonnegative integer such that a(n)! contains a string of exactly n consecutive 5's.
%C A254500 a(14) > 1500000. - _Jon E. Schoenfield_, Mar 31 2015
%e A254500 a(1) = 7 as 7! equals 5040, which contains '5' and 5 is the smallest integer for which the condition is met.
%t A254500 A254450[n_] := Module[{m = 0},
%t A254500 If[n == 0, While[MemberQ[IntegerDigits[m!], 5], m++]; m,
%t A254500 t = Table[5, n];
%t A254500 While[! MemberQ[Split[IntegerDigits[m!]], t], m++]; m]];
%t A254500 Table[A254450[n], {n, 0, 13}] (* _Robert Price_, Mar 21 2019 *)
%Y A254500 Cf. A254042, A254447, A254448, A254449, A254501, A254502, A254716, A254717.
%K A254500 nonn,more,base
%O A254500 0,2
%A A254500 _Martin Y. Champel_, Jan 31 2015
%E A254500 a(12)-a(13) from _Jon E. Schoenfield_, Feb 27 2015
%E A254500 a(0) prepended by _Jon E. Schoenfield_, Mar 01 2015
%E A254500 a(14)-a(15) from _Bert Dobbelaere_, Oct 29 2018