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%I #16 Aug 21 2021 13:13:39
%S 2,16,56,190,556,1821,4928,14136,39017,107405,291330,791513,2148323,
%T 5797898,15726486,42605113,115371428,312629484,847000031,2295700537,
%U 6223257066,16874397811,45764114391,124142354193,336811260666
%N Least number k such that round(k/pi(k)) = n.
%C a(n) is the index of the first occurrence of n in A107609.
%C Lim_{n->infinity} a(n+1)/a(n) ~ e.
%F a(n) = min { k >= 2 : round(k/pi(k)) = n }.
%e a(2) = 16 because round(16/pi(16)) = round(16/6) = 3 and for no number less than 16 does the quotient equal 3.
%t f[n_] := Round[ n / PrimePi[ n]]; g[2] = 2; g[n_] := g[n] = Block[{k = PrimePi[E g[n - 1]]}, While[ f[k] < n, k++ ]; k]; Do[ Print[ g[ n]], {n, 2, 26}]
%Y Cf. A000720, A107609, A107614, A272231.
%K nonn
%O 2,1
%A _Jonathan Vos Post_ and _Robert G. Wilson v_, May 17 2005
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