A113466 Least number that begins an n-term arithmetic progression with common difference 2 in which all terms have the same number of divisors.
1, 3, 3, 213, 213, 1383, 3091, 8129, 943607, 943607, 19235031, 21470685, 21470685, 21470685, 21470685
Offset: 1
Examples
a(4) = 213 because 213, 215, 217 and 219 each have 4 divisors.
Programs
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Mathematica
Module[{nn=21470695,ds},ds=Table[DivisorSigma[0,n],{n,1,nn,2}];2*Table[ SequencePosition[ds,PadRight[{},k,x_],1],{k,15}][[All,1]]][[All,1]]-1 (* Requires Mathematica version 10 or later *) (* The program will take a long time to run. To generate the first 8 terms of the sequence, change the nn constant to 8200 and the k range from 15 to 8 and the program will run quickly. *) (* Harvey P. Dale, Aug 16 2020 *)
Comments