

A240590


Number of primes between successive powerful numbers (A001694(n)).


2



2, 2, 0, 2, 3, 0, 2, 0, 4, 3, 2, 2, 3, 3, 2, 0, 1, 3, 5, 5, 2, 1, 1, 5, 1, 7, 0, 5, 2, 4, 5, 1, 5, 2, 7, 3, 2, 2, 6, 9, 4, 4, 0, 7, 8, 2, 7, 4, 4, 8, 1, 1, 4, 4, 9, 7, 2, 1, 9, 10, 6, 1, 0, 2, 0, 9, 12, 7, 4, 12, 6, 5, 4, 5, 12, 0, 8, 3, 3, 10, 8, 0, 2, 13, 2, 13, 10, 10, 1, 15, 0, 7, 9, 9, 3, 13, 7, 4, 0, 7, 5, 4, 13, 2
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..104.


EXAMPLE

a(9) = 4 because A001694(9) = 36, A001694(10) = 49, and there are 4 primes between them: 37, 41, 43 and 47.


PROG

(PARI)
ispowerful(n)={local(h); if(n==1, h=1, h=(vecmin(factor(n)[, 2])>1)); return(h)}
proxpowerful(n)={local(k); k=n+1; while(!ispowerful(k), k+=1); return(k)}
{for(i=1, 5000, if(ispowerful(i), m=proxpowerful(i); p=primepi(m)primepi(i); print(p)))}


CROSSREFS

Cf. A001694, A240591.
Sequence in context: A141661 A278521 A195910 * A080769 A328903 A143539
Adjacent sequences: A240587 A240588 A240589 * A240591 A240592 A240593


KEYWORD

nonn


AUTHOR

Antonio Roldán, Apr 08 2014


STATUS

approved



