OFFSET
1,1
COMMENTS
For each term given here except 5, k+2 is divisible by 3, but that's not always true: k=149784995358 is a counterexample. Also, k+2 is divisible by 5 for all terms here except 5 and 26206, but it is also not true for k=70333261.
LINKS
Vincenzo Librandi and Donovan Johnson, Table of n, a(n) for n = 1..500 (first 80 terms from Vincenzo Librandi)
MATHEMATICA
Do[If[DivisorSigma[1, n+2] == 2*DivisorSigma[1, n-2], Print[n]], {n, 2, 10^9}] (* Ryan Propper, Sep 26 2005 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 18 2002
EXTENSIONS
Edited by Dean Hickerson, Feb 20 2002
More terms from Ryan Propper, Sep 26 2005
STATUS
approved