Concatenation of n and n + 2 or {n,n+2}.

Terms

a(0) =13a(1) =24a(2) =35a(3) =46a(4) =57a(5) =68a(6) =79a(7) =810a(8) =911a(9) =1012a(10) =1113a(11) =1214a(12) =1315a(13) =1416a(14) =1517a(15) =1618a(16) =1719a(17) =1820a(18) =1921a(19) =2022a(20) =2123a(21) =2224a(22) =2325a(23) =2426a(24) =2527a(25) =2628a(26) =2729a(27) =2830a(28) =2931a(29) =3032