1,1
Table of n, a(n) for n=1..18.
2*2 + 1 = 5 (prime) so a(1)=2;
2*2*3 + 1 = 13 (prime) so a(2)=3;
2*2*3*5 + 1 = 61 (prime) so a(3)=5.
(Magma) [p:p in PrimesUpTo(4000)|IsPrime(2*&*PrimesUpTo(p)+1)]; // Marius A. Burtea, Mar 25 2019
Cf. A119833, A119835.
Sequence in context: A028867 A104154 A123214 * A095180 A101989 A098922
Adjacent sequences: A119831 A119832 A119833 * A119835 A119836 A119837
nonn,more
Pierre CAMI, May 25 2006
approved
