This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A264940 Lucky factor of n. 5
 0, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 7, 2, 0, 2, 3, 2, 0, 2, 9, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 7, 2, 3, 2, 0, 2, 13, 2, 3, 2, 0, 2, 0, 2, 3, 2, 15, 2, 9, 2, 3, 2, 7, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 0, 2, 3, 2, 0, 2, 7, 2, 3, 2, 21, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence is analogous to the smallest prime factor of n (A020639). If n is lucky, a(n)=0; if n is unlucky, a(n) is the number that rejects n from the lucky number sieve. This is 2 for even numbers, and a lucky number >= 3 for odd unlucky numbers. LINKS Max Barrentine, Table of n, a(n) for n = 1..10000 FORMULA From Antti Karttunen, Sep 11 2016: (Start) If A145649(n) = 1 [when n is lucky], a(n) = 0, else if n is even, a(n) = 2, otherwise a(n) = A000959(A265859(n)) = A000959(A260438(n)). For n >= 2, a(A219178(n)) = A000959(n). (End) PROG (Scheme) (define (A264940 n) (if (= 1 (A145649 n)) 0 (if (even? n) 2 (A000959 (A260438 n))))) ;; Antti Karttunen, Sep 11 2016 CROSSREFS Cf. A000959, A050505, A145649, A219178, A255543, A255545, A260438, A265859. Cf. A020639, A271419 (somewhat analogous sequences). Sequence in context: A202036 A246752 A246650 * A272800 A104513 A305610 Adjacent sequences:  A264937 A264938 A264939 * A264941 A264942 A264943 KEYWORD nonn AUTHOR Max Barrentine, Dec 09 2015 EXTENSIONS Formula corrected and comment clarified by Antti Karttunen, Sep 11 2016 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 July 23 13:58 EDT 2019. Contains 325254 sequences. (Running on oeis4.)