a(n)=(s(n)+4)/8, where s(n)=n-th base 8 palindrome that starts with 4.

Terms

a(0) =1a(1) =5a(2) =33a(3) =34a(4) =35a(5) =36a(6) =37a(7) =38a(8) =39a(9) =40a(10) =257a(11) =266a(12) =275a(13) =284a(14) =293a(15) =302a(16) =311a(17) =320a(18) =2049a(19) =2057a(20) =2065a(21) =2073a(22) =2081a(23) =2089a(24) =2097a(25) =2105a(26) =2114a(27) =2122a(28) =2130a(29) =2138