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 A240592 #15 Apr 17 2014 03:57:48 %S A240592 1,2,0,2,0,1,1,1,0,0,1,0,1,1,1,1,0,0,2,0,0,1,0,2,0,0,1,1,0,0,1,0,0,0, %T A240592 2,1,0,2,0,1,0,0,0,0,0,1,0,1,0,1,1,0,0,0,0,2,0,1,0,0,1,0,1,1,0,0,2,0, %U A240592 0,0,0,0,2,0,2,0,0,0,0,0,0,1,0,0,0,0,0,0 %N A240592 Number of primes between successive composite squarefree numbers (A120944). %C A240592 First positions where the numbers n=2..5 occur are at: 2, 142, 2180230, 256857823. - _Vaclav Kotesovec_, Apr 17 2014 %e A240592 a(4) is 2 because A120944(4)=15, A120944(5)=21, 2 primes between them: 17 and 19. %o A240592 (PARI) %o A240592 freesqrcomp(n)=issquarefree(n)&&!isprime(n) %o A240592 nextfqc(n)={local(k);k=n+1;while(!freesqrcomp(k),k+=1);return(k)} %o A240592 primesin(a,b)={local(p=a,q=0);while(p<b,p=nextprime(p);if(p<b,q+=1);p+=1);return(q)} %o A240592 {for(i=2,1000,if(freesqrcomp(i),m=nextfqc(i);p=primesin(i,m);print(p)))} %Y A240592 Cf. A120944, A240593. %K A240592 nonn %O A240592 1,2 %A A240592 _Antonio Roldán_, Apr 08 2014