OFFSET
1,1
COMMENTS
For odd primes p: a(p-1) = p; the converse is not true, as e.g. a(25-1)=25.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MATHEMATICA
epm[n_]:=Module[{m=n+1, epn2=2EulerPhi[n]}, While[EulerPhi[m]<epn2, m++]; m]; Array[epm, 70] (* Harvey P. Dale, Apr 13 2012 *)
PROG
(PARI) a(n)=my(t=2*eulerphi(n), m=max(n, t)); while(eulerphi(m++)<t, ); m \\ Charles R Greathouse IV, Feb 21 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Dec 22 2002
STATUS
approved