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 A340763 #15 Jun 10 2021 12:22:08 %S A340763 0,0,0,0,0,0,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4, %T A340763 4,4,5,5,5,5,5,5,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,8,8, %U A340763 8,8,8,8,9,9,9,9,9,9,10,10,10,10,10,10,10,10,10,10,10,10 %N A340763 Number of primes p <= n that are congruent to 1 modulo 3. %H A340763 Jianing Song, <a href="/A340763/b340763.txt">Table of n, a(n) for n = 1..10000</a> %F A340763 a(n) + A340764(n) = A000720(n) - 1 for n >= 3. %e A340763 There are 11 primes <= 100 that are congruent to 1 modulo 3, namely 7, 13, 19, 31, 37, 43, 61, 67, 73, 79, 97, so a(100) = 11. %o A340763 (PARI) a(n) = sum(i=1, n, isprime(i) && (i%3==1)) %Y A340763 Cf. A002476, A340764, A172104, A066339, A066490. %K A340763 nonn,easy %O A340763 1,13 %A A340763 _Jianing Song_, Apr 28 2021