n - reversal of base 4 digits of n (written in base 10).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =3a(5) =0a(6) =-3a(7) =-6a(8) =6a(9) =3a(10) =0a(11) =-3a(12) =9a(13) =6a(14) =3a(15) =0a(16) =15a(17) =0a(18) =-15a(19) =-30a(20) =15a(21) =0a(22) =-15a(23) =-30a(24) =15a(25) =0a(26) =-15a(27) =-30a(28) =15a(29) =0