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 A083535 #11 Aug 02 2012 16:36:34
%S A083535 0,1,2,2,4,4,6,6,6,6,8,8,11,11,11,11,14,14,17,17,17,17,20,20,20,20,20,
%T A083535 20,23,23,27,27,27,27,27,27,30,30,30,30,34,34,38,38,38,38,41,41,41,41,
%U A083535 41,41,45,45,45,45,45,45,50,50,54,54,54,54,54,54,58,58,58,58,62,62,66,66,66,66
%N A083535 A version of the Chebyshev function theta(n): a(n) = ceiling(Sum_{primes p <= n } log(p)).
%C A083535 See A035158, which is the main entry for this function.
%C A083535 The old entry with this sequence number was a duplicate of A083235.
%F A083535 a(n) ~ n by the prime number theorem. - _Charles R Greathouse IV_, Aug 02 2012
%K A083535 nonn
%O A083535 1,3
%A A083535 _N. J. A. Sloane_, Oct 02 2008