Unhappy numbers: numbers having period-8 2-digitized sequences.

Terms

a(0) =2a(1) =3a(2) =4a(3) =5a(4) =6a(5) =8a(6) =9a(7) =11a(8) =12a(9) =14a(10) =15a(11) =16a(12) =17a(13) =18a(14) =20a(15) =21a(16) =22a(17) =24a(18) =25a(19) =26a(20) =27a(21) =29a(22) =30a(23) =33a(24) =34a(25) =35a(26) =36a(27) =37a(28) =38a(29) =39