Concatenate prevprime(n) and n.

Terms

a(0) =23a(1) =34a(2) =35a(3) =56a(4) =57a(5) =78a(6) =79a(7) =710a(8) =711a(9) =1112a(10) =1113a(11) =1314a(12) =1315a(13) =1316a(14) =1317a(15) =1718a(16) =1719a(17) =1920a(18) =1921a(19) =1922a(20) =1923a(21) =2324a(22) =2325a(23) =2326a(24) =2327a(25) =2328a(26) =2329a(27) =2930a(28) =2931a(29) =3132