A240592 Number of primes between successive composite squarefree numbers (A120944).

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, 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, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0

Offset

1,2

Comments

First positions where the numbers n=2..5 occur are at: 2, 142, 2180230, 256857823. - Vaclav Kotesovec, Apr 17 2014

Links

Table of n, a(n) for n=1..88.

Example

a(4) is 2 because A120944(4)=15, A120944(5)=21, 2 primes between them: 17 and 19.

Prog

(PARI)
freesqrcomp(n)=issquarefree(n)&&!isprime(n)
nextfqc(n)={local(k); k=n+1; while(!freesqrcomp(k), k+=1); return(k)}
primesin(a, b)={local(p=a, q=0); while(p<b, p=nextprime(p); if(p<b, q+=1); p+=1); return(q)}
{for(i=2, 1000, if(freesqrcomp(i), m=nextfqc(i); p=primesin(i, m); print(p)))}

Crossrefs

Cf. A120944, A240593.

Sequence in context: A341021 A358331 A277142 * A001877 A339896 A112712

Adjacent sequences: A240589 A240590 A240591 * A240593 A240594 A240595

Keyword

nonn

Author

Antonio Roldán, Apr 08 2014

Status

approved