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.
%I A306870 #17 Mar 16 2019 17:16:07
%S A306870 2024,9504,62744,496320,573560,677144,1000824,1173704,1208504,1921185,
%T A306870 2140215,2198504,2312024,2580864,3847095,4012184,4682744,5416280,
%U A306870 6618080,9247095,12500865,12970880,13496840,14371104,23939685,25942784,26409320,28644704,34093304
%N A306870 Lesser of reduced bi-unitary amicable pair.
%C A306870 A pair m < n is a reduced bi-unitary amicable pair if bsigma(m) = bsigma(n) = m + n + 1, where bsigma(n) is the sum of bi-unitary divisors of n (A188999).
%C A306870 The larger members are in A306871.
%H A306870 Amiram Eldar, <a href="/A306870/b306870.txt">Table of n, a(n) for n = 1..528</a> (terms below 2*10^11, from David Moews's site).
%H A306870 David Moews, <a href="http://djm.cc/amicable.html">Perfect, amicable and sociable numbers</a>.
%e A306870 2024 is in the sequence since it is the lesser of the amicable pair (2024, 2295): bsigma(2024) = bsigma(2295) = 4320 = 2024 + 2295 + 1.
%t A306870 fun[p_, e_]:=If[OddQ[e], (p^(e+1)-1)/(p-1), (p^(e+1)-1)/(p-1)-p^(e/2)]; bsigma[1] = 1; bsigma[n_] := Times @@ (fun @@@ FactorInteger[n]); f[n_] := bsigma[n] - n - 1; s={}; Do[m = f[n]; If[m > n && f[m] == n, AppendTo[s, n]], {n, 1, 10^7}]; s
%Y A306870 Cf. A003502, A126172, A188999, A292980, A306871.
%K A306870 nonn
%O A306870 1,1
%A A306870 _Amiram Eldar_, Mar 14 2019