a(n)=(s(n)+6)/10, where s(n)=n-th base 10 palindrome that starts with 4.

Terms

a(0) =1a(1) =5a(2) =41a(3) =42a(4) =43a(5) =44a(6) =45a(7) =46a(8) =47a(9) =48a(10) =49a(11) =50a(12) =401a(13) =412a(14) =423a(15) =434a(16) =445a(17) =456a(18) =467a(19) =478a(20) =489a(21) =500a(22) =4001a(23) =4011a(24) =4021a(25) =4031a(26) =4041a(27) =4051a(28) =4061a(29) =4071