OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
12 is a term since sqrt(phi(19) * phi(20)) = sqrt(18 * 8) = sqrt(144) = 12.
MATHEMATICA
f[x_] := EulerPhi[x]; Do[s=Sqrt[f[n+1]*f[n]]; If[IntegerQ[s], Print[s]], {n, 1, 5000}]
Select[Sqrt[#]&/@(Times@@@Partition[EulerPhi[Range[3000]], 2, 1]), IntegerQ] (* Harvey P. Dale, Nov 04 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, May 21 2003
STATUS
approved