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A289132 Indices of records in A063974. 1
1, 12, 24, 60, 72, 216, 240, 720, 1440, 2160, 2880, 4320, 8640, 10080, 12960, 17280, 20160, 25920, 30240, 40320, 43200, 51840, 60480, 90720, 103680, 120960, 181440, 241920, 302400, 362880, 483840, 604800, 725760, 1088640, 1209600, 1451520, 1814400, 2419200 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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).

The unitary version of A145899.

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.

Is this a subsequence of A025487? - David A. Corneth, Jun 25 2017

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

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.

MATHEMATICA

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 *)

CROSSREFS

Cf. A025487, A034448, A063974, A145899.

Sequence in context: A247944 A123980 A097704 * A098585 A087105 A230355

Adjacent sequences:  A289129 A289130 A289131 * A289133 A289134 A289135

KEYWORD

nonn

AUTHOR

Amiram Eldar, Jun 25 2017

STATUS

approved

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Last modified December 8 14:38 EST 2019. Contains 329865 sequences. (Running on oeis4.)