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 A131540 #15 Jul 20 2024 22:19:13
%S A131540 0,4,46,157,222,220,2269,11019,18842,192918,192916,271979,1039316,
%T A131540 7193133,14060686,97428976
%N A131540 Exponent of least power of 2 having exactly n consecutive 6's in its decimal representation.
%H A131540 Popular Computing (Calabasas, CA), <a href="/A094776/a094776.jpg">Two Tables</a>, Vol. 1, (No. 9, Dec 1973), page PC9-16.
%e A131540 a(3)=157 because 2^157(i.e. 182687704666362864775460604089535377456991567872) is the smallest power of 2 to contain a run of 3 consecutive sixes in its decimal form.
%t A131540 a = ""; Do[ a = StringJoin[a, "6"]; b = StringJoin[a, "6"]; k = 1; While[ StringPosition[ ToString[2^k], a] == {} || StringPosition[ ToString[2^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]
%Y A131540 Cf. A006889, A131535, A131536, A131537, A131538, A131539, A131541, A131542, A131543.
%K A131540 more,nonn,base
%O A131540 0,2
%A A131540 _Shyam Sunder Gupta_, Aug 26 2007
%E A131540 Two more terms from _Sean A. Irvine_, May 31 2010
%E A131540 a(13)-a(14) from _Lars Blomberg_, Jan 24 2013
%E A131540 a(15) from _Bert Dobbelaere_, Mar 07 2019
%E A131540 a(0)=0 prepended by _Paul Geneau de Lamarlière_, Jul 20 2024