cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A339683 Larger of amicable pair a < b such that the ratio of their number of divisors d(b)/d(a) sets a new record.

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%I A339683 #4 Dec 12 2020 19:52:56
%S A339683 284,1210,486178,12361622,39944086,6119799324639,15309719733555,
%T A339683 36680009488425,20386078790473473,43160565196326158,
%U A339683 1052608596326926425,6924667299336450388
%N A339683 Larger of amicable pair a < b such that the ratio of their number of divisors d(b)/d(a) sets a new record.
%C A339683 The terms are ordered according to their lesser counterparts (A339682).
%C A339683 The terms were calculated using data from Chernykh's site.
%H A339683 Sergei Chernykh, <a href="http://sech.me/ap/">Amicable pairs list</a>.
%t A339683 s[n_] := DivisorSigma[1, n] - n; rm = 0; seq = {}; Do[m = s[n]; If[m > n && s[m] == n && (r = Divide @@ DivisorSigma[0, {m, n}]) > rm, rm = r; AppendTo[seq, m]], {n, 1, 10^7}]; seq
%Y A339683 Cf. A000005, A002025, A002046, A063990, A328255, A339682.
%K A339683 nonn,more
%O A339683 1,1
%A A339683 _Amiram Eldar_, Dec 12 2020