OFFSET
1,1
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..2500
MAPLE
with(numtheory);
P:=proc(i)
local f, n, p, pfs;
for n from 1 to i do
pfs:=ifactors(n)[2];
f:=n*add(op(2, p)/op(1, p), p=pfs);
if phi(n)=phi(f) then print(n); fi;
od;
end:
P(1000);
MATHEMATICA
d[0] = d[1] = 0; d[n_] := n*Total[f = FactorInteger[n]; f[[All, 2]]/f[[All, 1]] ]; Reap[For[n = 1, n < 6000, n++, If[EulerPhi[n] == EulerPhi[d[n]], Sow[n]]]][[2, 1]] (* Jean-François Alcover, Apr 22 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, May 10 2011
STATUS
approved