OFFSET
1,1
COMMENTS
We call the multiset {n,n,x,x} amicable iff sigma(n)=sigma(x)=n+n+x+x.
If the condition x!=n were dropped, the terms from A027687 would also belong here.
LINKS
John Cerkan, Table of n, a(n) for n = 1..1000
PROG
(PARI) isOK(n) = x=(sigma(n)-2*n)/2; x>0 && x!=n && denominator(x)==1 && sigma(x)==n+n+x+x
CROSSREFS
KEYWORD
nonn
AUTHOR
Jeppe Stig Nielsen, Jun 23 2015
STATUS
approved