The OEIS is supported by the many generous donors to the OEIS Foundation.

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

0

`%I #7 Feb 11 2022 19:17:58
`

`%S 1,5,41,42,43,44,45,46,47,48,49,50,401,412,423,434,445,456,467,478,
`

`%T 489,500,4001,4011,4021,4031,4041,4051,4061,4071,4081,4091,4102,4112,
`

`%U 4122,4132,4142,4152,4162,4172,4182,4192,4203,4213
`

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

`%t (#+6)/10&/@Select[Range[50000],PalindromeQ[#]&&IntegerDigits[#][[1]]==4&] (* _Harvey P. Dale_, Feb 11 2022 *)
`

`%K nonn,base
`

`%O 1,2
`

`%A _Clark Kimberling_
`