a(n)=(s(n)+8)/10, where s(n)=n-th base 10 palindrome that starts with 2.

Terms

a(0) =1a(1) =3a(2) =21a(3) =22a(4) =23a(5) =24a(6) =25a(7) =26a(8) =27a(9) =28a(10) =29a(11) =30a(12) =201a(13) =212a(14) =223a(15) =234a(16) =245a(17) =256a(18) =267a(19) =278a(20) =289a(21) =300a(22) =2001a(23) =2011a(24) =2021a(25) =2031a(26) =2041a(27) =2051a(28) =2061a(29) =2071