A122444 - OEIS

%I #7 Mar 04 2017 10:12:38

%S 1,2,3,3,5,7,5,2,7,11,5,13,11,17,7,3,19,13,23,7,17,11,19,29,31,2,13,

%T 23,37,11,3,41,17,43,29,13,31,47,19,5,53,37,23,59,17,11,61,41,43,19,

%U 67,47,71,13,29,73,31,79,53,23,83

%N Greatest prime factor of powers of semiprimes.

%C A122443 is least prime factor of powers of semiprimes. Cf. A076397 Largest prime factor of n-th perfect power.

%H Michael De Vlieger, <a href="/A122444/b122444.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A006530(A085155(n)) = greatest prime factor of A085155 powers of semiprimes.

%t FactorInteger[#][[-1, 1]] & /@ Select[Range@ 168, Function[n, Or[n == 1, And[Length@ # == 1, EvenQ@ First@ #], And[Length@ # == 2, SameQ @@ #]] &[FactorInteger[n][[All, -1]]]]] (* _Michael De Vlieger_, Mar 04 2017 *)

%Y Cf. A000040, A001358, A006530, A020639, A076396, A076397, A085155, A122443.

%K easy,nonn

%O 1,2

%A _Jonathan Vos Post_, Sep 06 2006