A061469 GCD of the amicable pairs: a(n) = gcd(A002025(n), A002046(n)).

4, 2, 4, 4, 8, 8, 105, 16, 92, 16, 135, 819, 10, 45, 585, 16, 8, 10, 16, 16, 8, 44, 4, 4, 14, 8, 16, 98, 16, 585, 8, 8, 8, 8, 8, 4, 8, 105, 16, 8, 135, 8, 10, 50, 10, 5733, 8, 585, 10, 855, 16, 10, 4, 10, 10, 585, 32, 10, 8, 16, 14, 8, 16, 4, 8, 310, 8, 16, 8, 10, 50, 855, 14, 8, 10

Offset

1,1

Comments

The pairs are ordered by the smaller number. - David Wasserman, Jun 18 2002

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

Eric Weisstein's World of Mathematics, Amicable Pair.

Example

a(1) = gcd(220, 284) = 4;
a(2) = gcd(1184, 1210) = 2.

Mathematica

With[{s = PositionIndex@ Array[DivisorSigma[1, #] &, 10^6]}, Flatten@ Map[GCD @@ # &, Apply[Join, Map[Function[n, Select[Subsets[Lookup[s, n], {2}], Total@ # == n &]], Sort@ Select[Keys@ s, Length@ Lookup[s, #] > 1 &]]]]] (* Michael De Vlieger, Oct 22 2017 *)

Crossrefs

Cf. A002025, A002046, A259180 (amicable pairs).

Sequence in context: A057697 A019921 A204617 * A222641 A368437 A258852

Adjacent sequences: A061466 A061467 A061468 * A061470 A061471 A061472

Keyword

nonn

Author

Jason Earls, Jun 11 2001

Extensions

More terms from David Wasserman, Jun 18 2002

a(22) corrected by T. D. Noe, Aug 15 2010

Status

approved