Digital root of n (repeatedly add the digits of n until a single digit is reached).

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =8a(9) =9a(10) =1a(11) =2a(12) =3a(13) =4a(14) =5a(15) =6a(16) =7a(17) =8a(18) =9a(19) =1a(20) =2a(21) =3a(22) =4a(23) =5a(24) =6a(25) =7a(26) =8a(27) =9a(28) =1a(29) =2