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Infinitary barely deficient numbers: infinitary deficient numbers whose infinitary abundancy is closer to 2 than that of any smaller infinitary deficient number.
1

%I #6 Jul 14 2020 21:37:52

%S 1,2,8,84,110,128,1155,3680,6490,8200,8648,12008,18632,32768,724000,

%T 1495688,2095208,3214090,3477608,3660008,5076008,12026888,16102808,

%U 26347688,29322008,33653888,73995392,615206030,815634435,2147483648,42783299288,80999455688

%N Infinitary barely deficient numbers: infinitary deficient numbers whose infinitary abundancy is closer to 2 than that of any smaller infinitary deficient number.

%C The infinitary abundancy of a number k is isigma(k)/k, where isigma is the sum of infinitary divisors of k (A049417).

%C The corresponding values of the infinitary abundancy are 1, 1.5, 1.875, 1.904..., 1.963..., ...

%e 8 is a term since it is infinitary deficient (A129657), and isigma(8)/8 = 15/8 is higher than isigma(k)/k for all the infinitary deficient numbers k < 8.

%t fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ fun @@@ FactorInteger[n]; seq = {}; r = 0; Do[s = isigma[n]/n; If[s < 2 && s > r, AppendTo[seq, n]; r = s], {n, 1, 10^6}]; seq

%Y Cf. A049417, A129657, A335054.

%Y Similar sequences: A228450, A262228, A302572, A307122, A336253.

%K nonn

%O 1,2

%A _Amiram Eldar_, Jul 14 2020