OFFSET
1,1
COMMENTS
Orders of cycles are 4,4,1,4,1,4,4,4,4,2,2,2,1,2,4,4,4,4,4,4,4,4,...
LINKS
Eric Weisstein's World of Mathematics, Sociable Numbers
EXAMPLE
{51,-30,132,72} is a {2,1}-Aliquot cycle.
MATHEMATICA
fQ[n_] := Nest[ DivisorSigma[1, # ] - 2# &, n, 4] == n; t = {}; Do[ If[ fQ[n], AppendTo[t, n]], {n, 3*10^7}]; t (* Robert G. Wilson v *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Yasutoshi Kohmoto, Jan 27 2006
EXTENSIONS
a(12)-a(22) from Robert G. Wilson v, Jan 30 2006
a(23)-a(29) from Charles R Greathouse IV, Nov 13 2010
STATUS
approved