a(n)=(s(n)+3)/10, where s(n)=n-th base 10 palindrome that starts with 7.

Terms

a(0) =1a(1) =8a(2) =71a(3) =72a(4) =73a(5) =74a(6) =75a(7) =76a(8) =77a(9) =78a(10) =79a(11) =80a(12) =701a(13) =712a(14) =723a(15) =734a(16) =745a(17) =756a(18) =767a(19) =778a(20) =789a(21) =800a(22) =7001a(23) =7011a(24) =7021a(25) =7031a(26) =7041a(27) =7051a(28) =7061a(29) =7071