A276440 - OEIS

%I #9 Sep 12 2016 17:02:05

%S 1,2,3,2,5,3,7,2,3,5,11,3,13,7,5,2,17,3,1,5,7,11,23,3,25,13,3,7,29,5,

%T 1,2,11,17,7,3,37,2,13,5,41,7,43,11,5,23,47,3,7,25,17,13,53,3,11,7,3,

%U 29,1,5,61,2,7,2,13,11,67,17,23,7,71,3,1,37,25,2,77,13,1,5,3,41,83,7,17,43,29,11,89,5,91,23,3,47

%N a(n) = greatest ludic number (A003309) that divides n.

%H Antti Karttunen, <a href="/A276440/b276440.txt">Table of n, a(n) for n = 1..10001</a>

%H <a href="/index/Si#sieve">Index entries for sequences generated by sieves</a>

%e a(19) = 1 as 19 is not a ludic number, but it is a prime, thus only ludic number that divides it is the very first one A003309(1) = 1.

%e a(589) = 1 also as 589 = 19*31 and both 19 and 31 are in A192505.

%o (Scheme)

%o (define (A276440 n) (let loop ((k 1) (mt 1)) (let ((t (A003309 k))) (cond ((> t n) mt) ((zero? (modulo n t)) (loop (+ 1 k) t)) (else (loop (+ 1 k) mt))))))

%Y Cf. A003309, A192505, A272565, A276568, A276569.

%Y Differs from A006530 for the first time at n=19.

%K nonn

%O 1,2

%A _Antti Karttunen_, Sep 11 2016