login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A099634 a(n) = gcd(P+p, P*p) where P is the largest and p the smallest prime factor of n. 3
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 (list; graph; refs; listen; history; text; internal format)
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 A090369

Adjacent sequences:  A099631 A099632 A099633 * A099635 A099636 A099637

KEYWORD

nonn

AUTHOR

Labos Elemer, Oct 28 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 23 19:41 EDT 2020. Contains 337315 sequences. (Running on oeis4.)