OFFSET
1,1
COMMENTS
This sequence is a subsequence of A066198.
MATHEMATICA
de[n_]:=DivisorSigma[1, n]-EulerPhi[n]; Do[If[de[n]==de[n+1], Print[n]], {n, 50000000}] (* Firoozbakht *)
Select[Range[10^6], (EulerPhi[# + 1] - EulerPhi[#]) == (DivisorSigma[1, # + 1] - DivisorSigma[1, #]) &] (* Alonso del Arte, Feb 08 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Farideh Firoozbakht, Nov 01 2008
EXTENSIONS
a(9)-a(16) from Donovan Johnson, Dec 14 2009
a(17)-a(24) from Donovan Johnson, Feb 08 2012
STATUS
approved