a(n)=(s(n)+3)/8, where s(n)=n-th base 8 palindrome that starts with 5.

Terms

a(0) =1a(1) =6a(2) =41a(3) =42a(4) =43a(5) =44a(6) =45a(7) =46a(8) =47a(9) =48a(10) =321a(11) =330a(12) =339a(13) =348a(14) =357a(15) =366a(16) =375a(17) =384a(18) =2561a(19) =2569a(20) =2577a(21) =2585a(22) =2593a(23) =2601a(24) =2609a(25) =2617a(26) =2626a(27) =2634a(28) =2642a(29) =2650