a(n) = largest prime < lcm(1..n).

Terms

a(0) =5a(1) =11a(2) =59a(3) =59a(4) =419a(5) =839a(6) =2503a(7) =2503a(8) =27701a(9) =27701a(10) =360337a(11) =360337a(12) =360337a(13) =720703a(14) =12252197a(15) =12252197a(16) =232792559a(17) =232792559a(18) =232792559a(19) =232792559a(20) =5354228879a(21) =5354228879a(22) =26771144371a(23) =26771144371a(24) =80313433159a(25) =80313433159