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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 (list; graph; refs; listen; history; text; internal format)
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

Antti Karttunen, Table of n, a(n) for n = 1..10000

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.

Cf. A006530, A020639, A066048, A252459, A252757.

Sequence in context: A168181 A324732 A164980 * A168182 A204447 A188642

Adjacent sequences:  A252369 A252370 A252371 * A252373 A252374 A252375

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

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Last modified May 25 15:24 EDT 2019. Contains 323572 sequences. (Running on oeis4.)