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 A053821 #4 Mar 30 2012 16:48:45
%S A053821 0,1,1,1,2,2,2,1,1,3,2,2,3,3,3,1,3,2,3,3,3,3,3,2,2,4,1,3,3,4,3,1,3,4,
%T A053821 4,2,4,4,4,3,4,4,4,3,3,4,4,2,2,3,4,4,4,2,4,3,4,4,4,4,4,4,3,1,5,4,4,4,
%U A053821 4,5,4,2,4,5,3,4,4,5,4,3,1,5,4,4,5,5,4,3,4,4,5,4,4
%N A053821 A discrete approximation to log(n): Sum_{ d divides n } A029833(d).
%C A053821 For n >= 1, log(n) = Sum_{ d divides n } Lambda(d), where Lambda is the real Mangoldt function (see A029833).
%D A053821 T. M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 32, Cf. Theorem 2.10.
%K A053821 nonn,easy
%O A053821 1,5
%A A053821 _N. J. A. Sloane_, Apr 08 2000