login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A113466 Least number that begins an n-term arithmetic progression with common difference 2 in which all terms have the same number of divisors. 2
1, 3, 3, 213, 213, 1383, 3091, 8129, 943607, 943607, 19235031, 21470685, 21470685, 21470685, 21470685 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Second column of A113465. Next term is > 6368300000.
LINKS
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
Sequence in context: A152418 A273925 A113457 * A007301 A009715 A344283
KEYWORD
nonn,less,hard
AUTHOR
David Wasserman, Jan 08 2006
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)