OFFSET
1,1
COMMENTS
Because numbers of the form 1+A000668(.) are a subsequence, 162259276829213363391578010288128 and 170141183460469231731687303715884105728 are also in the sequence (not necessarily the next ones). - Joerg Arndt, Jul 01 2012
MATHEMATICA
f[n_]:=Plus@@Divisors[Plus@@Divisors[n]-n]==n; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 9!}]; lst (* Vladimir Joseph Stephan Orlovsky, May 14 2010 *)
Select[Range[550000], DivisorSigma[1, DivisorSigma[1, #]-#]==#&] (* The program generates the first 7 terms of the sequence. Increasing the Range constant will generate more but it will run a long time. *) (* Harvey P. Dale, May 08 2018 *)
PROG
(PARI) isok(n) = sigma(sigma(n)-n) == n; \\ Michel Marcus, May 06 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Benoit Cloitre, Jul 27 2002
EXTENSIONS
a(6) inserted by Jaroslav Krizek, Jun 29 2012
STATUS
approved