Jacobsthal sequence (A001045) as represented in base 4.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =11a(5) =23a(6) =111a(7) =223a(8) =1111a(9) =2223a(10) =11111a(11) =22223a(12) =111111a(13) =222223a(14) =1111111a(15) =2222223a(16) =11111111a(17) =22222223a(18) =111111111a(19) =222222223a(20) =1111111111a(21) =2222222223a(22) =11111111111a(23) =22222222223a(24) =111111111111a(25) =222222222223