Smallest prime > n!! (double factorial of n).

Terms

a(0) =2a(1) =3a(2) =5a(3) =11a(4) =17a(5) =53a(6) =107a(7) =389a(8) =947a(9) =3847a(10) =10399a(11) =46091a(12) =135151a(13) =645131a(14) =2027033a(15) =10321937a(16) =34459429a(17) =185794579a(18) =654729139a(19) =3715891217a(20) =13749310577a(21) =81749606417a(22) =316234143227