A052369 - OEIS

%I #22 Sep 08 2022 08:44:59

%S 2,3,2,3,5,3,7,5,2,3,5,7,11,3,5,13,3,7,5,2,11,17,7,3,19,13,5,7,11,5,

%T 23,3,7,5,17,13,3,11,7,19,29,5,31,7,2,13,11,17,23,7,3,37,5,19,11,13,5,

%U 3,41,7,17,43,29,11,5,13,23,31,47,19,3,7,11,5,17,13,7,53,3,11,37,7,19,23

%N Largest prime factor of n, where n runs through composite numbers.

%H Robert Israel, <a href="/A052369/b052369.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A006530(A002808(n)). [_Reinhard Zumkeller_, Aug 25 2008]

%e First composite is 4, largest prime factor is 2, so a(1)=2.

%p map(t -> max(numtheory:-factorset(t)), remove(isprime,[$2..10^3])); # _Robert Israel_, Aug 10 2014

%t FactorInteger[#][[-1,1]]&/@Select[Range[150],CompositeQ] (* _Harvey P. Dale_, Jan 24 2016 *)

%o (Magma) [ D[ #D]: n in [2..115] | not IsPrime(n) where D is PrimeDivisors(n) ]; // [_Klaus Brockhaus_, Jun 23 2009]

%o (PARI) forcomposite(n=1, 1e2, p=factor(n)[omega(n), 1]; print1(p, ", ")) \\ _Felix Fröhlich_, Aug 08 2014

%Y Cf. A002808, A006530, A056608. [From _Reinhard Zumkeller_, Aug 25 2008]

%K nonn,easy

%O 1,1

%A Michael Contente (mec1000(AT)aol.com), Mar 08 2000

%E More terms from _James A. Sellers_, Mar 09 2000