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 A217189 #8 Nov 23 2013 13:52:28
%S A217189 1,6,27,61,146,148,1658,5220,28595,51790
%N A217189 a(n) is the number of digits in the decimal representation of the smallest power of 7 that contains n consecutive identical digits.
%C A217189 Number of digits in 7^k is equal to floor(1 + k*log_10(7)).
%t A217189 k = 0; Join[{1}, Table[While[d = IntegerDigits[7^k]; prt = Partition[Differences[d], n - 1, 1]; ! MemberQ[prt, Table[0, {n - 1}]], k++]; Length[d], {n, 2, 8}]] (* _T. D. Noe_, Oct 03 2012 *)
%Y A217189 Cf. A215730, A215736.
%K A217189 nonn,base
%O A217189 1,2
%A A217189 _V. Raman_, Sep 27 2012
%E A217189 a(10) added by _V. Raman_, Nov 23 2013