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A289132 Indices of records in A063974. 2

%I

%S 1,12,24,60,72,216,240,720,1440,2160,2880,4320,8640,10080,12960,17280,

%T 20160,25920,30240,40320,43200,51840,60480,90720,103680,120960,181440,

%U 241920,302400,362880,483840,604800,725760,1088640,1209600,1451520,1814400,2419200

%N Indices of records in A063974.

%C Numbers n such that usigma(x) = n has more solutions x than any smaller n, where usigma(x) is the sum of unitary divisors of x (A034448).

%C The unitary version of A145899.

%C The corresponding number of solutions for each term is: 1, 2, 3, 4, 6, 7, 11, 18, 27, 30, 32, 48, 63, 65, 71, 88, 89, 102, 121, 122, 131, 144, 188, 190, 203, 262, 313, 364, 377, 472, 483, 584, 668, 725, 810, 928, 1076, 1138.

%C Is this a subsequence of A025487? - _David A. Corneth_, Jun 25 2017

%H Amiram Eldar, <a href="/A289132/b289132.txt">Table of n, a(n) for n = 1..53</a>

%e There are 3 solutions to usigma(x) = 24: usigma(14) = usigma(15) = usigma(23) = 24. For all m < 24, there are 2 or fewer solutions to usigma(x) = m, thus 24 is in the sequence.

%t usigma[n_] := Block[{d = Divisors[n]}, Plus @@ Select[d, GCD[#, n/#] == 1 &]]; t = Map[usigma, Range[10^7]]; t2 = Sort[Tally[t]]; mn = 0; t3 = {}; Do[If[t2[[n]][[2]] > mn, mn = t2[[n]][[2]]; AppendTo[t3, t2[[n]][[1]]]], {n, Length[t2]}]; t3 (* after _T. D. Noe_ at A145899 *)

%Y Cf. A025487, A034448, A063974, A145899.

%K nonn

%O 1,2

%A _Amiram Eldar_, Jun 25 2017

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Last modified January 29 16:58 EST 2020. Contains 331347 sequences. (Running on oeis4.)