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 A131547 #8 Mar 04 2019 17:20:20
%S A131547 8,33,34,275,1385,539,8881,22792,90785,107188,704996,1847533,5756980,
%T A131547 9995031,68353788
%N A131547 Least power of 3 having exactly n consecutive 6's in its decimal representation.
%e A131547 a(3)=34 because 3^34(i.e. 16677181699666569) is the smallest power of 3 to contain a run of 3 consecutive sixes in its decimal form.
%t A131547 a = ""; Do[ a = StringJoin[a, "6"]; b = StringJoin[a, "6"]; k = 1; While[ StringPosition[ ToString[3^k], a] == {} || StringPosition[ ToString[3^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]
%Y A131547 Cf. A195269, A131552, A131551, A131550, A131549, A131548, A131546, A131545, A131544.
%K A131547 more,nonn,base
%O A131547 1,1
%A A131547 _Shyam Sunder Gupta_, Aug 26 2007
%E A131547 a(11)-a(14) from _Lars Blomberg_, Feb 02 2013
%E A131547 a(15) from _Bert Dobbelaere_, Mar 04 2019