a(n) is the smallest positive integer x such that x^2 - n! is prime.

Terms

a(0) =2a(1) =2a(2) =3a(3) =11a(4) =19a(5) =31a(6) =79a(7) =209a(8) =607a(9) =1921a(10) =6337a(11) =21907a(12) =78913a(13) =295289a(14) =1143539a(15) =4574149a(16) =18859733a(17) =80014841a(18) =348776611a(19) =1559776279a(20) =7147792823a(21) =33526120127a(22) =160785623627a(23) =787685471389