OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
FORMULA
sigma(9356- phi(9356)) = sigma(9356 - 4676) = 16380 = sigma(9356).
MAPLE
with(numtheory); P:=proc(q) local n; for n from 1 to q do
if sigma(n)=sigma(n-phi(n)) then print(n); fi; od; end: P(10^9);
MATHEMATICA
Select[Range[10^6], DivisorSigma[1, #] == DivisorSigma[1, # - EulerPhi@ #] &] (* Michael De Vlieger, Jun 21 2016 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paolo P. Lava, Jun 21 2016
STATUS
approved