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 A337030 #8 Aug 12 2020 03:18:57 %S A337030 0,0,0,1,2,2,4,4,6,7,8,11,13,14,15,16,19,19,22,24,24,27,28,31,35,35, %T A337030 36,38,38,40,46,48,50,51,56,56,58,61,63,64,67,67,73,73,75,75,82,90,91, %U A337030 91,93,96,96,99,102,105,108,108,110,111,112,117,124,126,126,127 %N A337030 a(n) is the number of squarefree composite numbers < prime(n). %H A337030 Hugo Pfoertner, <a href="/A337030/b337030.txt">Table of n, a(n) for n = 1..10000</a> %F A337030 a(1) = 0; a(n+1) = a(n) + A061398(n-1) for n>1. %e A337030 a(1) = a(2) = a(3) = 0 because the only composite number < 5 is the square 4. %e A337030 a(4) = 1: 6 is the first squarefree composite number < prime(4) = 7. %o A337030 (PARI) m=0;pp=0;forprime(p=2,320,forcomposite(c=pp,p,if(issquarefree(c),m++));print1(m,", ");pp=p) %Y A337030 Cf. A061398, A120944. %K A337030 nonn %O A337030 1,5 %A A337030 _Hugo Pfoertner_, Aug 11 2020