OFFSET
1,1
EXAMPLE
sigma(5) = 6 = 4 + 2 = phi(5) + phi(5-1), so 5 is a term of the sequence.
MATHEMATICA
Select[Range[2, 10^5], EulerPhi[ # ] + EulerPhi[ # - 1] == DivisorSigma[1, # ] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Feb 19 2002
EXTENSIONS
a(9)-a(31) from Donovan Johnson, Mar 01 2012
STATUS
approved