{n concatenate R(n)} + {R(n) concatenate n}, where R(n) = digit reversal of n.

Terms

a(0) =0a(1) =22a(2) =44a(3) =66a(4) =88a(5) =110a(6) =132a(7) =154a(8) =176a(9) =198a(10) =1111a(11) =2222a(12) =3333a(13) =4444a(14) =5555a(15) =6666a(16) =7777a(17) =8888a(18) =9999a(19) =11110a(20) =2222a(21) =3333a(22) =4444a(23) =5555a(24) =6666a(25) =7777a(26) =8888a(27) =9999a(28) =11110a(29) =12221