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 A000879 #50 Apr 21 2024 23:01:19 %S A000879 2,4,9,15,30,39,61,72,99,146,162,219,263,283,329,409,487,519,609,675, %T A000879 705,811,886,1000,1163,1252,1294,1381,1423,1523,1877,1976,2141,2190, %U A000879 2489,2547,2729,2915,3043,3241,3436,3512,3868,3945,4089,4164,4627,5106 %N A000879 Number of primes < prime(n)^2. %C A000879 a(n) is the least index i such that A052180(i) = prime(n). - _Labos Elemer_, May 14 2003 %C A000879 Number of primes determined at the n-th step of the sieve of Eratosthenes. - _Jean-Christophe Hervé_, Oct 21 2013 %C A000879 There are only 3 squares in the current data: 4, 9, 7745089. - _Michel Marcus_, Apr 07 2018 %C A000879 There are no other squares up to a(780000). - _Giovanni Resta_, Apr 09 2018 %H A000879 Donovan Johnson, <a href="/A000879/b000879.txt">Table of n, a(n) for n = 1..10000</a> %F A000879 a(n) = A000720(A001248(n)). - _Michel Marcus_, Apr 07 2018 %t A000879 PrimePi[Prime[Range[50]]^2] (* _Harvey P. Dale_, Jan 16 2013 *) %o A000879 (PARI) a(n) = primepi(prime(n)^2); \\ _Michel Marcus_, Oct 28 2013 %Y A000879 Cf. A050216 (first differences), A089609, A052180, A000720, A001248, A000885, A054270 (primes of rank a(n)). %K A000879 nonn %O A000879 1,1 %A A000879 gandalf(AT)hrn.office.ssi.net (James D. Ausfahl) %E A000879 Edited by _Ralf Stephan_, Aug 24 2004