OFFSET
1,1
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..200
MATHEMATICA
Select[Range[10^6], DivisorSigma[1, #-2] + DivisorSigma[1, #+2] == DivisorSigma[1, 2*#] &] (* Amiram Eldar, May 13 2022 *)
PROG
(PARI) s1=1; s2=3; s3=4; s4=7; for(n=3, 10^9, s5=sigma(n+2); if(s1+s5==sigma(2*n), print(n)); s1=s2; s2=s3; s3=s4; s4=s5) \\ Donovan Johnson, Sep 17 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 18 2002
EXTENSIONS
a(19)-a(33) from Donovan Johnson, Jan 31 2009
STATUS
approved