A119986 - OEIS

%I #5 Sep 01 2020 12:01:02

%S 1,6,19,5,6,17,6,6,10,2,15,17,3,9,7,48,32,12,39,9,17,18,27,1,50,36,18,

%T 3,11,44,19,45,46,78,36,36,5,20,33,41,127,42,12,63,16,33,31,42,8,6,98,

%U 57,21,47,22,91,21,45,24,1,3,12,72,57,51,129,351,8,23,87,88,108,80,120,4,3

%N Least positive k such that k * 10^n + prime(n) is prime.

%D J. Earls & J. Rogers, 0.1361015212836455566..., Lulu Press, NY, 2006, p. 22.

%H Amazon.com, <a href="http://tinyurl.com/o7qlb">0.1361015212836455566...(Title of split novel)</a>

%t lpk[n_]:=Module[{k=1,c=10^n,p=Prime[n]},While[!PrimeQ[k*c+p],k++];k]; Array[ lpk,80,4] (* _Harvey P. Dale_, Sep 01 2020 *)

%K easy,nonn

%O 4,2

%A _Jason Earls_, Aug 03 2006