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 A061568 #15 Jul 02 2018 03:33:14
%S A061568 1,3,4,7,9,13,16,21,25,31,37,45,51,60,66,75,85,95,103,115,127,138,150,
%T A061568 162,177,191,205,219,233,250,267,283,300,319,338,360,376,400,421,441,
%U A061568 461,481,509,531,557,578,602,630,653,684,707,737,765,793,825,853,884
%N A061568 Number of primes <= sum of first n primes.
%H A061568 Harry J. Smith, <a href="/A061568/b061568.txt">Table of n, a(n) for n = 1..1000</a>
%F A061568 a(n) = A000720(A007504(n)). - _Michel Marcus_, Jul 02 2018
%t A061568 PrimePi/@FoldList[Plus, 0, Prime[Range[50]]]//Rest
%o A061568 (PARI) { default(primelimit, 3682913); n=0; s=0; forprime (p=2, prime(1000), s+=p; write("b061568.txt", n++, " ", primepi(s)) ) } \\ _Harry J. Smith_, Jul 24 2009
%o A061568 (PARI) a(n) = primepi(sum(k=1, n, prime(k))); \\ _Michel Marcus_, Jul 02 2018
%Y A061568 Cf. A000849, A000720, A007504.
%K A061568 easy,nonn
%O A061568 1,2
%A A061568 _Harvey P. Dale_, May 18 2001