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 A239012 #26 Jan 22 2020 14:44:51
%S A239012 0,2,3,6,10,11,19,35,127,131,175,207,1235,2470,2651,1241310,1922910,
%T A239012 471056338,1001431598,1720335627,4203146094,5353516238,21838571507,
%U A239012 25770284079,40822793867
%N A239012 Exponents m such that the decimal expansion of 7^m exhibits its first zero from the right later than any previous exponent.
%C A239012 Assume that a zero precedes all decimal expansions. This will take care of those cases in A030703.
%C A239012 Inspired by the seqfan list discussion Re: "possible sequence", beginning with David Wilson 7:57 PM Mar 06 2014 and continued by _M. F. Hasler_, _Allan C. Wechsler_ and _Franklin T. Adams-Watters_.
%t A239012 f[n_] := Position[ Reverse@ Join[{0}, IntegerDigits[ PowerMod[7, n, 10^500]]], 0, 1, 1][[1, 1]]; k = mx = 0; lst = {}; While[k < 500000001, c = f[k]; If[c > mx, mx = c; AppendTo[ lst, k]; Print@ k]; k++]; lst
%Y A239012 Cf. A000420, A030703, A020665, A031142, A239008, A239009, A239010, A239011, A239013, A239014, A239015.
%K A239012 nonn,base,more
%O A239012 1,2
%A A239012 _Charles R Greathouse IV_ and _Robert G. Wilson v_, Mar 14 2014
%E A239012 a(19)-a(22) from _Bert Dobbelaere_, Jan 21 2019
%E A239012 a(23)-a(25) from _Chai Wah Wu_, Jan 15 2020