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 A120357 #13 Apr 03 2023 10:36:11
%S A120357 2,31,331,3319,33223,332191,3321937,33219281,332192831,3321928097,
%T A120357 33219280951,332192809589,3321928094941,33219280948907,
%U A120357 332192809488739,3321928094887411,33219280948873687,332192809488736253
%N A120357 a(n) is the smallest prime p such that 2^p-1 (a Mersenne number) contains 10^n or more decimal digits.
%C A120357 For n>0 almost all digits of a(n) from the left are equal to the first terms of the expansion Log[10]/Log[2] = {3, 3, 2, 1, 9, 2, 8, 0, 9, 4, 8, 8, 7, 3, 6, 2, 3, 4, 7, 8, 7, 0, 3, 1, 9, 4, 2, 9, 4, 8, 9, 3, 9, ...} = A020862(n). - _Alexander Adamchuk_, Jan 16 2007
%H A120357 Farideh Firoozbakht, <a href="/A120357/b120357.txt">Table of n, a(n) for n = 0..29</a>
%H A120357 G. L. Honaker, Jr. and Chris Caldwell, <a href="https://t5k.org/curios/cpage/13130.html">Prime Curios! 33219281</a>
%H A120357 Author?, <a href="http://www.mersenne.org/prize.htm">GIMPS</a> [Broken link?]
%e A120357 E.g. a(7)=33219281 because 2^33219281-1 is the smallest Mersenne number that contains 10^7 (ten million) or more decimal digits.
%Y A120357 Cf. A001348.
%Y A120357 Cf. A020862 = decimal expansion of log(10)/log(2).
%K A120357 base,nonn
%O A120357 0,1
%A A120357 _G. L. Honaker, Jr._, Jun 25 2006
%E A120357 More terms from _Farideh Firoozbakht_, Jul 22 2006