OFFSET
1,1
COMMENTS
Suggested by N. J. A. Sloane and Robert G. Wilson v.
a(6) > 10^12.
a(7) > 10^13. - Giovanni Resta, Mar 29 2013
a(7) > 10^18. - Hiroaki Yamanouchi, Aug 21 2018
Any term x of this sequence can be combined with any term y of A223610 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable. - Timothy L. Tiffin, Sep 13 2016
EXAMPLE
n = 33624064. sigma(n)-2*n = -18.
MATHEMATICA
Select[Range[1, 10^8], DivisorSigma[1, #] - 2 # == - 18 &] (* Vincenzo Librandi, Sep 14 2016 *)
PROG
(PARI) for(n=1, 10^8, if(sigma(n)-2*n==-18, print1(n ", ")))
(Magma) [n: n in [1..9*10^6] | (SumOfDivisors(n)-2*n) eq -18]; // Vincenzo Librandi, Sep 14 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Donovan Johnson, Mar 23 2013
EXTENSIONS
a(6) from Giovanni Resta, Mar 29 2013
STATUS
approved