A141710 Least prime factor of n-th Carmichael number A002997(n).

3, 5, 7, 5, 7, 7, 7, 5, 7, 13, 7, 13, 7, 3, 7, 11, 7, 13, 7, 17, 7, 7, 41, 5, 37, 13, 19, 13, 31, 41, 5, 37, 31, 13, 13, 3, 11, 7, 7, 5, 7, 11, 7, 19, 7, 5, 7, 43, 31, 37, 17, 23, 7, 31, 41, 11, 19, 17, 13, 53, 5, 7, 11, 43, 13, 5, 29, 5, 101, 53, 7, 13, 11, 7, 19, 31, 41, 13, 29, 31, 5

Offset: 1

Author

M. F. Hasler, Jul 01 2008

Keywords

• nonn

Comments

All terms of this sequence are odd primes. See A002997 for references.

Examples

			a(1)=3 since A002997(1)=3*11*17.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• OEIS index entries for Carmichael numbers

Crossrefs

Cf. A002997, A020639, A081702, A135717.

Programs

Mathematica

CarmichaelQ[n_] := Not[PrimeQ[n]] && Divisible[n - 1, CarmichaelLambda[n]]; FactorInteger[#][[1, 1]]& /@ Select[Range[4, 10^7], CarmichaelQ] (* Jean-François Alcover, Sep 23 2011 *)

PARI

A141710(n)=vecmin(factor(A002997(n))[,1]) /* where A002997(n) can be defined as follows: */ system("wget b002997.txt; sed -e 's/^[0-9]*//' b002997.gp"); A2997=readvec("b002997.gp"); A002997(n)=A2997[n]; \

Formula

a(n) = A020639(A002997(n))