A052369 Largest prime factor of n, where n runs through composite numbers.

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, 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, 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

Offset: 1

Author

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

Keywords

• nonn
• easy

Examples

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

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002808, A006530, A056608. [From Reinhard Zumkeller, Aug 25 2008]

Programs

Magma

[ D[ #D]: n in [2..115] | not IsPrime(n) where D is PrimeDivisors(n) ]; // [Klaus Brockhaus, Jun 23 2009]

Maple

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

Mathematica

FactorInteger[#][[-1,1]]&/@Select[Range[150],CompositeQ] (* Harvey P. Dale, Jan 24 2016 *)

PARI

forcomposite(n=1, 1e2, p=factor(n)[omega(n), 1]; print1(p, ", ")) \\ Felix Fröhlich, Aug 08 2014

Formula

a(n) = A006530(A002808(n)). [Reinhard Zumkeller, Aug 25 2008]

Extensions

More terms from James Sellers, Mar 09 2000