A Jacobsthal sequence (A078008) to base 4.

Terms

a(0) =1a(1) =0a(2) =2a(3) =2a(4) =12a(5) =22a(6) =112a(7) =222a(8) =1112a(9) =2222a(10) =11112a(11) =22222a(12) =111112a(13) =222222a(14) =1111112a(15) =2222222a(16) =11111112a(17) =22222222a(18) =111111112a(19) =222222222a(20) =1111111112a(21) =2222222222a(22) =11111111112a(23) =22222222222a(24) =111111111112a(25) =222222222222