a(n) is the smallest prime of the form k*lcm(1..n) - 1.

Terms

a(0) =2a(1) =3a(2) =5a(3) =11a(4) =59a(5) =59a(6) =419a(7) =839a(8) =5039a(9) =5039a(10) =55439a(11) =55439a(12) =1081079a(13) =1081079a(14) =1081079a(15) =1441439a(16) =24504479a(17) =24504479a(18) =232792559a(19) =232792559a(20) =232792559a(21) =232792559a(22) =5354228879a(23) =5354228879a(24) =53542288799a(25) =53542288799