Number of letters in the n-th ordinal number (in American English).

Terms

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