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%I #20 Apr 23 2017 23:55:53
%S 1,4,12,60,420,4620,60060,1021020,19399380,446185740,12939386460,
%T 401120980260,14841476269620,608500527054420,26165522663340060,
%U 1229779565176982820,65178316954380089460,3845520700308425278140,234576762718813941966540,15716643102160534111758180
%N Smallest m such that A097249(m) = n; from n=1 onwards, twice the primorials, 2*A002110(n).
%C A097249(a(n))=n and A097249(m)<n for m<a(n).
%C a(n) = A088860(n) for n>=1. - _G. C. Greubel_, Apr 23 2017
%H Vincenzo Librandi, <a href="/A097250/b097250.txt">Table of n, a(n) for n = 0..200</a>
%H <a href="/index/Pri#primorial_numbers">Index entries for sequences related to primorial numbers</a>
%F a(n) = if n=0 then 1 else 2*A002110(n).
%t Join[{1}, 2 Denominator[Accumulate[1/Prime[Range[20]]]]] (* _Vincenzo Librandi_, Mar 25 2017 *)
%t Join[{1}, 2*FoldList[Times, 1, Prime[Range[50]]]] (* _G. C. Greubel_, Apr 23 2017 *)
%Y Cf. A002110, A088860, A097249.
%Y From a(1)=4 onwards, row 3 of A276945.
%K nonn
%O 0,2
%A _Reinhard Zumkeller_, Aug 03 2004
%E Name amended by _Antti Karttunen_, Sep 24 2016
%E a(18)-a(19) from _Vincenzo Librandi_, Mar 25 2017