A113466 - OEIS

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

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OFFSET

1,2

COMMENTS

Second column of A113465. Next term is > 6368300000.

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

a(4) = 213 because 213, 215, 217 and 219 each have 4 divisors.

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 *)

CROSSREFS

Cf. A113457, A113465.

Sequence in context: A152418 A273925 A113457 * A007301 A009715 A344283

Adjacent sequences: A113463 A113464 A113465 * A113467 A113468 A113469

KEYWORD

nonn,less,hard

AUTHOR

David Wasserman, Jan 08 2006

STATUS

approved