Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #16 May 13 2022 04:54:38
%S 4,16,272,284,604,4556,6904,8413,10463,12070,19004,23290,26284,29944,
%T 40312,44252,107557,114616,230987,239134,276476,332022,343793,403196,
%U 501008,762078,771130,893606,1013348,1160192,1731290,1807016,2066404
%N Numbers k such that sigma(k-2) + sigma(k+2) = sigma(2k).
%H Donovan Johnson, <a href="/A067172/b067172.txt">Table of n, a(n) for n = 1..200</a>
%t Select[Range[10^6], DivisorSigma[1, #-2] + DivisorSigma[1, #+2] == DivisorSigma[1, 2*#] &] (* _Amiram Eldar_, May 13 2022 *)
%o (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
%Y Cf. A000203, A067730.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Feb 18 2002
%E a(19)-a(33) from _Donovan Johnson_, Jan 31 2009