A099634 a(n) = gcd(P+p, P*p) where P is the largest and p the smallest prime factor of n.

4, 3, 4, 5, 1, 7, 4, 3, 1, 11, 1, 13, 1, 1, 4, 17, 1, 19, 1, 1, 1, 23, 1, 5, 1, 3, 1, 29, 1, 31, 4, 1, 1, 1, 1, 37, 1, 1, 1, 41, 1, 43, 1, 1, 1, 47, 1, 7, 1, 1, 1, 53, 1, 1, 1, 1, 1, 59, 1, 61, 1, 1, 4, 1, 1, 67, 1, 1, 1, 71, 1, 73, 1, 1, 1, 1, 1, 79, 1, 3, 1, 83, 1, 1, 1, 1, 1, 89, 1, 1, 1, 1, 1, 1, 1, 97

Offset

2,1

Links

Table of n, a(n) for n=2..97.

Example

If n is prime q > 2, then a(n) = gcd(q^2, 2q) = q.

Mathematica

PrimeFactors[n_Integer] := Flatten[ Table[ # [[1]], {1}] & /@ FactorInteger[n]]; f[n_] := Block[{pf = PrimeFactors[n]}, GCD[pf[[1]] + pf[[ -1]], pf[[1]]*pf[[ -1]] ]]; Table[ f[n], {n, 2, 97}] (* Robert G. Wilson v, Nov 04 2004 *)

Crossrefs

Sequence in context: A204671 A204816 A204818 * A203144 A109382 A342843

Adjacent sequences: A099631 A099632 A099633 * A099635 A099636 A099637

Keyword

nonn

Author

Labos Elemer, Oct 28 2004

Status

approved