OFFSET
1,3
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
MAPLE
gcpd := proc(a, b) local g , d ; g := 1 ; for d in numtheory[divisors](a) intersect numtheory[divisors](b) do if isprime(d) then g := max(g, d) ; end if; end do: g ; end proc:
A082065 := proc(n) gcpd( numtheory[phi](n), numtheory[sigma][2](n) ) ; end proc:
seq(A082065(n), n=1..120) ; # R. J. Mathar, Jul 09 2011
MATHEMATICA
Table[FactorInteger[GCD[EulerPhi@ n, DivisorSigma[2, n]]][[-1, 1]], {n, 100}] (* Michael De Vlieger, Jul 22 2017 *)
PROG
(PARI) gpf(n)=if(n>1, my(f=factor(n)[, 1]); f[#f], 1)
a(n)=gpf(gcd(eulerphi(n), sigma(n, 2))) \\ Charles R Greathouse IV, Feb 21 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Apr 07 2003
EXTENSIONS
Values corrected by R. J. Mathar, Jul 09 2011
Changed "was found" to "exists" in definition. - N. J. A. Sloane, Jan 29 2022
STATUS
approved