OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[200], IntegerQ[Product[EulerPhi[i], {i, 1, #}]/#] &] (* Carl Najafi, Aug 19 2011 *)
nn=150; With[{ep=Rest[FoldList[Times, 1, EulerPhi[Range[nn]]]]}, Flatten[ Position[Table[ep[[i]]/i, {i, nn}], _?IntegerQ]]] (* Harvey P. Dale, May 12 2012 *) (* this program is more than 200 times faster than the first Mathematica program above *)
PROG
(PARI) isok(n)=prod(k=1, n, eulerphi(k))%n==0 \\ Anders Hellström, Aug 22 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, Oct 03 2008
EXTENSIONS
More terms from Carl Najafi, Aug 19 2011
STATUS
approved