A115074 a(n) is the largest prime dividing the n-th nonsquarefree positive integer.

2, 2, 3, 3, 2, 3, 5, 3, 5, 3, 7, 2, 3, 5, 11, 5, 3, 7, 5, 13, 3, 7, 5, 7, 2, 17, 3, 5, 19, 5, 3, 7, 11, 5, 23, 3, 7, 11, 5, 13, 3, 7, 29, 13, 5, 11, 31, 5, 7, 2, 11, 5, 17, 7, 3, 7, 37, 5, 19, 17, 13, 5, 3, 41, 7, 13, 19, 43, 7, 11, 5, 23, 47, 7, 3, 7, 11, 5, 17, 23, 13, 53, 3, 11, 7, 5, 19, 29, 13

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A006530(A013929(n)).

Example

12, the 4th nonsquarefree positive integer, is 2^2 * 3. 3 is the largest prime dividing 12. So a(4) = 3.

Maple

with(numtheory): a:=proc(n) if mobius(n)=0 then op(nops(factorset(n)), factorset(n)) fi end: seq(a(n), n=1..270); # Emeric Deutsch, Mar 06 2006

Mathematica

FactorInteger[ # ][[ -1, 1]] & /@ Select[ Range@235, !SquareFreeQ@# &] (* Robert G. Wilson v, Mar 09 2006 *)

Crossrefs

Cf. A117183, A115090, A013929, A006530.

Sequence in context: A048687 A308621 A308623 * A234399 A214749 A239330

Adjacent sequences: A115071 A115072 A115073 * A115075 A115076 A115077

Keyword

nonn

Author

Leroy Quet, Mar 01 2006

Extensions

More terms from Emeric Deutsch and Robert G. Wilson v, Mar 06 2006

Status

approved