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I am trying to find a formula for the $n$th term of a sequence of rational numbers less than 1. Regardless of how many terms I include in the table, FindSequenceFunction copies the input as the output. Perhaps my sequence is too complicated, but I would like to know if there are any other methods or functions which help find the $n$th term of a sequence.

Here's the code for the sorted table:

sopf[n_] := Plus @@ (First /@ FactorInteger[n])
Composite[n_Integer] := FixedPoint[n + PrimePi[#] + 1 &, n]
Sort[Table[
1 - ((1 + sopf[Composite[j]] - PrimeNu[Composite[j]])/
Composite[j]), {j, 1, 30}]]

With output

*{1/3, 2/5, 3/7, 5/11, 6/13, 8/17, 9/19, 1/2, 8/15, 4/7, 20/33, 8/13,
2/3, 2/3, 24/35, 7/10, 5/7, 8/11, 11/15, 3/4, 16/21, 7/9, 4/5, 5/6,
38/45, 17/20, 7/8, 8/9, 8/9, 15/16}*
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4
  • $\begingroup$ try oeis.org perhaps $\endgroup$
    – pdmclean
    Commented Oct 21, 2017 at 22:00
  • $\begingroup$ @pdmclean that only works for integers. $\endgroup$ Commented Oct 21, 2017 at 22:26
  • 1
    $\begingroup$ Yes, but you can search the sequence of numerators and the sequence of denominators separately. $\endgroup$ Commented Oct 26, 2017 at 13:11
  • $\begingroup$ I tried, they didn't match any sequence in their database. $\endgroup$ Commented Oct 27, 2017 at 1:58

1 Answer 1

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This is how to answer any stupid question about finite sequences in pre-employment testing:

a = Sort[RandomInteger[{1, 100}, 20]];
f = Interpolation[a];
Show[
 ListPlot[a],
 Plot[f[t], {t, 1, Length[a]}]
 ]
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