A097250 Smallest m such that A097249(m) = n; from n=1 onwards, twice the primorials, 2*A002110(n).

1, 4, 12, 60, 420, 4620, 60060, 1021020, 19399380, 446185740, 12939386460, 401120980260, 14841476269620, 608500527054420, 26165522663340060, 1229779565176982820, 65178316954380089460, 3845520700308425278140, 234576762718813941966540, 15716643102160534111758180

Offset: 0

Author

Reinhard Zumkeller, Aug 03 2004

Keywords

• nonn

Comments

A097249(a(n))=n and A097249(m)

a(n) = A088860(n) for n>=1. - G. C. Greubel, Apr 23 2017

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200
• Index entries for sequences related to primorial numbers

Crossrefs

Cf. A002110, A088860, A097249.

From a(1)=4 onwards, row 3 of A276945.

Programs

Mathematica

Join[{1}, 2 Denominator[Accumulate[1/Prime[Range[20]]]]] (* Vincenzo Librandi, Mar 25 2017 *)
Join[{1}, 2*FoldList[Times, 1, Prime[Range[50]]]] (* G. C. Greubel, Apr 23 2017 *)

Formula

a(n) = if n=0 then 1 else 2*A002110(n).

Extensions

Name amended by Antti Karttunen, Sep 24 2016

a(18)-a(19) from Vincenzo Librandi, Mar 25 2017

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