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Least k such that floor[(10^n)/k] is prime.
3

%I #7 Jul 09 2018 23:02:05

%S 2,9,12,13,28,19,7,27,12,13,17,74,17,14,82,66,36,44,9,36,21,13,9,90,7,

%T 19,149,51,321,35,12,14,140,13,28,42,34,36,153,155,133,46,73,106,162,

%U 109,122,42,62,422,29,231,38,34,340,295,151,197,94,19,17,83,131,66,36

%N Least k such that floor[(10^n)/k] is prime.

%e a(1) = 2 as 10/2 = 5 is a prime. a(3) = 12 as floor[1000/12] = 83 is prime.

%t lkp[n_]:=Module[{k=2,c=10^n},While[!PrimeQ[Floor[c/k]],k++];k]; Array[ lkp,70] (* _Harvey P. Dale_, Jul 09 2018 *)

%Y Cf. A090518, A090519, A090520.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Dec 07 2003

%E Corrected and extended by Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Jan 28 2004

%E Further terms from _David Wasserman_, Dec 20 2005