Take sum of squares of digits of previous term, starting with 2.

Terms

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