%I #18 Jan 15 2022 17:04:14
%S 2,3,5,11,59,59,419,839,5039,5039,55439,55439,1081079,1081079,1081079,
%T 1441439,24504479,24504479,232792559,232792559,232792559,232792559,
%U 5354228879,5354228879,53542288799,53542288799,1044074631599
%N a(n) is the smallest prime of the form k*lcm(1..n) - 1.
%H Harvey P. Dale, <a href="/A083685/b083685.txt">Table of n, a(n) for n = 1..500</a>
%e a(9) = 5039: lcm(1..9) = 2520; 2519 is not a prime but 2*2520 - 1 = 5039 is a prime.
%t spf[n_]:=Module[{c=LCM@@Range[n],k=1},While[!PrimeQ[k*c-1],k++];k*c-1]; Array[spf,30] (* _Harvey P. Dale_, Jan 15 2022 *)
%o (PARI) a(n) = {my(lcmn = lcm(vector(n, k, k)), k = 1); while(!isprime(p = k*lcmn-1), k++); p;} \\ _Michel Marcus_, Mar 15 2018
%Y Cf. A070858.
%K nonn
%O 1,1
%A _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 15 2003
%E Corrected and extended by _Vladeta Jovovic_, Jun 16 2003