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A063975
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Smallest numbers such that the number of terms in inverse set usigma equals n; where usigma[] = A034448.
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0
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1, 12, 24, 60, 120, 72, 216, 288, 1320, 480, 240, 840, 1296, 2700, 960, 1512, 1080, 720, 1728, 2016, 3840, 3240, 3456, 2520, 3360, 3024, 1440, 3600, 6912, 2160, 19152, 2880, 7920, 13680, 9072, 12600, 6048, 5040, 18000, 6480, 27216, 13440, 7200, 27648, 5760
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| usigma[x]=288, invusigma[288]={138, 154, 165, 168, 213, 235, 248, 253}, so a(288)=8, the number of all terms in the inverse set and all similar numbers are larger:{288, 648, 672, 900}.
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MAPLE
| with(numtheory): A034448 := proc(n) option remember: local ans, i: ans:=1: for i from 1 to nops(ifactors(n)[2]) do ans := ans*(1+ifactors(n)[ 2 ][ i ][ 1 ]^ifactors(n)[ 2 ] [ i ] [ 2 ]): od: return ans: end: for n from 1 to 5000 do m:=A034448(n): if(type(ct[m], integer))then ct[m]:=ct[m]+1: else ct[m]:=1: fi:od: for m from 1 to 28 do for n from 1 to 5000 do if(ct[n]=m)then printf("%d, ", n):break: fi: od:od: # Nathaniel Johnston, Apr 29 2011
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CROSSREFS
| Cf. A051444, A054973, A057637, A034444, A034448.
Sequence in context: A097704 A098585 A087105 * A001335 A206026 A145899
Adjacent sequences: A063972 A063973 A063974 * A063976 A063977 A063978
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Sep 05 2001
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EXTENSIONS
| a(9) - a(45) from Nathaniel Johnston (nathaniel(AT)nathanieljohnston.com), Apr 29 2011
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