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A061469
GCD of the amicable pairs: a(n) = gcd(A002025(n), A002046(n)).
5
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
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