First (leftmost) digit - second digit + third digit - fourth digit .... = 11.

Terms

a(0) =209a(1) =308a(2) =319a(3) =407a(4) =418a(5) =429a(6) =506a(7) =517a(8) =528a(9) =539a(10) =605a(11) =616a(12) =627a(13) =638a(14) =649a(15) =704a(16) =715a(17) =726a(18) =737a(19) =748a(20) =759a(21) =803a(22) =814a(23) =825a(24) =836a(25) =847a(26) =858a(27) =869a(28) =902a(29) =913