Take sum of squares of digits of previous term; start with 5.

Terms

a(0) =5a(1) =25a(2) =29a(3) =85a(4) =89a(5) =145a(6) =42a(7) =20a(8) =4a(9) =16a(10) =37a(11) =58a(12) =89a(13) =145a(14) =42a(15) =20a(16) =4a(17) =16a(18) =37a(19) =58a(20) =89a(21) =145a(22) =42a(23) =20a(24) =4a(25) =16a(26) =37a(27) =58a(28) =89a(29) =145