cp's OEIS Frontend

A122144 Numbers k such that q(k) = M(k) where q(n) is the largest prime divisor of k and M(k) is the largest prime power divisor of k.

%I A122144 #16 May 23 2024 04:27:36
%S A122144 2,3,5,6,7,10,11,13,14,15,17,19,20,21,22,23,26,28,29,30,31,33,34,35,
%T A122144 37,38,39,41,42,43,44,46,47,51,52,53,55,57,58,59,60,61,62,65,66,67,68,
%U A122144 69,70,71,73,74,76,77,78,79,82,83,84,85,86,87,88,89,91,92,93,94,95,97,99
%N A122144 Numbers k such that q(k) = M(k) where q(n) is the largest prime divisor of k and M(k) is the largest prime power divisor of k.
%C A122144 Similar to A048839, the first difference occurs when n = 40.
%H A122144 Amiram Eldar, <a href="/A122144/b122144.txt">Table of n, a(n) for n = 1..10000</a>
%t A122144 Select[Range[2, 100], Max[Power @@@ (f = FactorInteger[#])] == f[[-1, 1]] &] (* _Amiram Eldar_, May 23 2024 *)
%o A122144 (PARI) isok(k) = {my(f = factor(k), pm = 0); if(k > 1, for(i = 1, #f~, pm = max(pm, f[i, 1]^f[i, 2])); pm == f[#f~, 1], 0);} \\ _Amiram Eldar_, May 23 2024
%Y A122144 Cf. A006530, A034699, A048839, A122145, A122146.
%K A122144 nonn
%O A122144 1,1
%A A122144 Douglas Stones (dssto1(AT)student.monash.edu.au), Aug 22 2006
%E A122144 Edited by _Ray Chandler_, Aug 23 2006