OFFSET
1,1
EXAMPLE
phi(314) + phi(316) = 156 + 156 = 312 = 1/2 sigma(315), so 315 belongs to the sequence.
MATHEMATICA
Select[Range[2, 10^5], EulerPhi[ # - 1] + EulerPhi[ # + 1] == (1/2)DivisorSigma[1, # ] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Oct 23 2002
EXTENSIONS
a(8)-a(30) from Donovan Johnson, Mar 01 2012
STATUS
approved