A259306 Numbers n such that there exists an x!=n that makes {n,n,x,x} an amicable multiset.

1441440, 1860768, 3205440, 3378240, 3423420, 3914820, 4029480, 4437720, 5738040, 6093360, 6807240, 7136640, 7239120, 7551360, 9402120, 10204740, 12270720, 12405120, 12942720, 13495680, 14627340, 14725620, 15233400, 17166240, 18097800, 19158048, 23023440

Offset: 1

Author

Jeppe Stig Nielsen, Jun 23 2015

Keywords

• nonn

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

Crossrefs

Cf. A027687, A259307, A259302, A259303, A259304, A259305, A036471.

Programs

PARI

isOK(n) = x=(sigma(n)-2*n)/2; x>0 && x!=n && denominator(x)==1 && sigma(x)==n+n+x+x