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 A138864 #8 Aug 04 2018 02:39:11 %S A138864 3,7,31,127,819,131,524,214,230,618,162,170,686,531,104,147,446,259, %T A138864 190,285,478,346,281,431,448,402,854,536,521,512,746,174,129,412,814, %U A138864 623,127,437,924,125,299,122,315,124,202,169,316 %N A138864 First 3 digits of n-th Mersenne prime A000668(n). %H A138864 L. C. Noll, <a href="http://www.isthe.com/chongo/tech/math/prime/mersenne.html">Mersenne Prime Digits and Names</a>. %Y A138864 Cf. A000668, A080173, A104511, A138863, A138864, A138865, A138866. %K A138864 base,nonn %O A138864 1,1 %A A138864 _Omar E. Pol_, Apr 02 2008 %E A138864 a(40)-a(47) from _Ivan Panchenko_, Aug 03 2018