OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..218 (all terms up to 5 million)
MATHEMATICA
Select[Range[11000], Divisible[DivisorSigma[1, #]+DivisorSigma[1, #+1], EulerPhi[ #]]&] (* Harvey P. Dale, Jul 16 2018 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 20 2002
EXTENSIONS
First two terms prepended by Harvey P. Dale, Jul 16 2018
STATUS
approved