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%I #9 Aug 06 2014 09:20:24
%S 1,1,2,1,1,1,3,2,1,1,40,1,1,10,10,10,7,17,4,11,15,10,11,54,24,8,11,2,
%T 18,2,6,4,58,3,14,15,1,3,13,16,1,37,4,4,8,11,80,2,37,58,55,34,15,59,
%U 26,1,32,42,47,56,47,4,57,62,27,18,14,17,12,47,19,16,39,9,71,13,6,6,25,10,1,1
%N Least k such that (10^k)*(P(n)#) - 1 is prime with P(i)= i-th prime and P(i)#= i-th primorial.
%e (10^1)*2 -1 = 19 prime so k(1)=1.
%e (10^1)*6 -1 = 59 prime so k(2)=1.
%e (10^2)*30 -1 = 2999 prime so k(3)=2.
%o (PARI) a(n) = {prd = prod(i=1, n, prime(i)); k = 1; while (!isprime(10^k*prd-1), k++); k;} \\ _Michel Marcus_, Aug 06 2014
%Y Cf. A002110.
%K nonn
%O 1,3
%A _Pierre CAMI_, Dec 15 2004
%E Corrected by _Michel Marcus_, Aug 06 2014