

A272565


Ludic factor of n.


13



1, 2, 3, 2, 5, 2, 7, 2, 3, 2, 11, 2, 13, 2, 3, 2, 17, 2, 5, 2, 3, 2, 23, 2, 25, 2, 3, 2, 29, 2, 7, 2, 3, 2, 5, 2, 37, 2, 3, 2, 41, 2, 43, 2, 3, 2, 47, 2, 5, 2, 3, 2, 53, 2, 11, 2, 3, 2, 7, 2, 61, 2, 3, 2, 5, 2, 67, 2, 3, 2, 71, 2, 13, 2, 3, 2, 77, 2, 5, 2, 3
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

This sequence is somewhat analogous to the smallest prime factor of n (A020639). However, each natural number has only one ludic factor, because once it is crossed off in the kth step of the sieve process, it is not a member of the terms considered in the (k+1)th step.


LINKS

Max Barrentine, Table of n, a(n) for n = 1..10000
OEIS Wiki, Ludic numbers.
Index entries for sequences generated by sieves


FORMULA

From Antti Karttunen, Sep 11 2016: (Start)
a(n) = A003309(1+A260738(n)).
For all n >= 1, a(A276347(n)) = A020639(A276347(n)).
(End).


PROG

(Scheme) (define (A272565 n) (A003309 (+ 1 (A260738 n)))) ;; Antti Karttunen, Sep 11 2016


CROSSREFS

Cf. A003309, A020639, A027748, A192607, A255127, A260738, A276440, A276568, A276569.
Cf. A276347, A276447, A276448 (ludic factor is equal, less than or greater than the smallest prime factor).
Cf. A264940 (analogous version for lucky numbers).
Sequence in context: A085308 A209190 A086286 * A135679 A092028 A020639
Adjacent sequences: A272562 A272563 A272564 * A272566 A272567 A272568


KEYWORD

nonn


AUTHOR

Max Barrentine, May 09 2016


STATUS

approved



