Periods of sum of fourth powers of digits iterated until the sequence becomes periodic.

Terms

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