a(n) = least prime > binomial(2n, n).

Terms

a(0) =2a(1) =3a(2) =7a(3) =23a(4) =71a(5) =257a(6) =929a(7) =3433a(8) =12889a(9) =48623a(10) =184777a(11) =705437a(12) =2704157a(13) =10400603a(14) =40116607a(15) =155117551a(16) =601080433a(17) =2333606281a(18) =9075135317a(19) =35345263801a(20) =137846528921a(21) =538257874499