The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 16 18:53 EDT 2021. Contains 343050 sequences. (Running on oeis4.)