OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
FORMULA
phi(a(n)) = x^2, a(n) - phi(a(n)) = y^2, a(n) is not an odd power of prime from A002496.
EXAMPLE
An even term is 2340 = 4*9*5*13 (phi = 576 = 24^2 and cototient = 1764 = 42^2).
An odd term is 14841 = 9*17*97 (phi = 9216 = 96^2, cototient = 5625 = 75^2).
MATHEMATICA
Select[ Range[ 1, 200000 ], IntegerQ[ Sqrt[ eu[ # ] ] ]&& IntegerQ[ Sqrt[ co[ # ] ] ]&&!Equal[ lfi[ # ], 1 ]& ], where eu[ x_ ] =EulerPhi[ x ], co[ x_ ]=x-EulerPhi[ x ] and lfi[ x_ ]=Length[ FactorInteger[ x ] ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Apr 25 2000
STATUS
approved