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

%I A061469 #36 Feb 16 2025 08:32:44
%S A061469 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,
%T A061469 8,16,98,16,585,8,8,8,8,8,4,8,105,16,8,135,8,10,50,10,5733,8,585,10,
%U A061469 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
%N A061469 GCD of the amicable pairs: a(n) = gcd(A002025(n), A002046(n)).
%C A061469 The pairs are ordered by the smaller number. - _David Wasserman_, Jun 18 2002
%H A061469 Amiram Eldar, <a href="/A061469/b061469.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
%H A061469 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AmicablePair.html">Amicable Pair</a>.
%e A061469 a(1) = gcd(220, 284) = 4;
%e A061469 a(2) = gcd(1184, 1210) = 2.
%t A061469 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 *)
%Y A061469 Cf. A002025, A002046, A259180 (amicable pairs).
%K A061469 nonn
%O A061469 1,1
%A A061469 _Jason Earls_, Jun 11 2001
%E A061469 More terms from _David Wasserman_, Jun 18 2002
%E A061469 a(22) corrected by _T. D. Noe_, Aug 15 2010