a(n)=(s(n)+2)/9, where s(n)=n-th base 9 palindrome that starts with 7.

Terms

a(0) =1a(1) =8a(2) =64a(3) =65a(4) =66a(5) =67a(6) =68a(7) =69a(8) =70a(9) =71a(10) =72a(11) =568a(12) =578a(13) =588a(14) =598a(15) =608a(16) =618a(17) =628a(18) =638a(19) =648a(20) =5104a(21) =5113a(22) =5122a(23) =5131a(24) =5140a(25) =5149a(26) =5158a(27) =5167a(28) =5176a(29) =5186