Squares written in base 4.

Terms

a(0) =0a(1) =1a(2) =10a(3) =21a(4) =100a(5) =121a(6) =210a(7) =301a(8) =1000a(9) =1101a(10) =1210a(11) =1321a(12) =2100a(13) =2221a(14) =3010a(15) =3201a(16) =10000a(17) =10201a(18) =11010a(19) =11221a(20) =12100a(21) =12321a(22) =13210a(23) =20101a(24) =21000a(25) =21301a(26) =22210a(27) =23121a(28) =30100a(29) =31021