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A252372
Characteristic function for A251726: a(n) = 1 if n > 1 and gpf(n) < spf(n)^2, otherwise 0; here spf(n) and gpf(n) (smallest and greatest prime factor of n) are sequences A020639(n) and A006530(n).
5
0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0
OFFSET
1
COMMENTS
a(n) = 1 if n > 1 and there exists r <= A006530(n) such that r^k <= A020639(n) and A006530(n) < r^(k+1) for some k >= 0, otherwise 0 (the original definition).
LINKS
FORMULA
Other identities. For all n >= 1:
a(n) = a(A066048(n)). [The result depends only on the smallest and the largest prime factor of n.]
PROG
(Scheme) (define (A252372 n) (if (< (A252375 n) (+ 1 (A006530 n))) 1 0))
CROSSREFS
Characteristic function of A251726.
A252373 gives the partial sums.
Sequence in context: A368916 A324732 A164980 * A168182 A204447 A368905
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 17 2014. A new simpler definition found Jan 04 2015 and the original definition moved to the Comments section.
STATUS
approved