OFFSET
1,1
COMMENTS
If n is present, then so is also 2*n.
If n = p_1^e_1*p_2^e_2*... with p_1 > p_2 > ..., then n is in this sequence iff p_1^2 > p_2 and e_1 = 1. - Charlie Neder, Jun 13 2019
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
EXAMPLE
10 = 2*5 is present, because 2^2 < 5 and 5 is a prime.
20 = 2*10 is present, because 2^2 < 10, and 10 itself is present in the sequence.
PROG
(Haskell)
a245729 n = a245729_list !! (n-1)
a245729_list = filter f [1..] where
f x = p ^ 2 < q && (a010051' q == 1 || f q)
where q = div x p; p = a020639 x
(Scheme, with Antti Karttunen's IntSeq-library)
(define (charfun_for_A245729 n) (if (and (> (A001222 n) 1) (> (A032742 n) (A000290 (A020639 n)))) (+ (A010051 (A032742 n)) (charfun_for_A245729 (A032742 n))) 0))
;; Antti Karttunen, Jan 16 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen and Reinhard Zumkeller, Jan 09 2015
STATUS
approved