This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A264940 #33 Sep 12 2016 17:01:17 %S A264940 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, %T A264940 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, %U A264940 2,0,2,3,2,0,2,0,2,3,2,0,2,7,2,3,2,21,2 %N A264940 Lucky factor of n. %C A264940 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. %H A264940 Max Barrentine, <a href="/A264940/b264940.txt">Table of n, a(n) for n = 1..10000</a> %F A264940 From _Antti Karttunen_, Sep 11 2016: (Start) %F A264940 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)). %F A264940 For n >= 2, a(A219178(n)) = A000959(n). %F A264940 (End) %o A264940 (Scheme) (define (A264940 n) (if (= 1 (A145649 n)) 0 (if (even? n) 2 (A000959 (A260438 n))))) ;; _Antti Karttunen_, Sep 11 2016 %Y A264940 Cf. A000959, A050505, A145649, A219178, A255543, A255545, A260438, A265859. %Y A264940 Cf. A020639, A271419 (somewhat analogous sequences). %K A264940 nonn %O A264940 1,2 %A A264940 _Max Barrentine_, Dec 09 2015 %E A264940 Formula corrected and comment clarified by _Antti Karttunen_, Sep 11 2016