Replacing digits d in decimal expansion of n with d^3 yields a square.

Terms

a(0) =0a(1) =1a(2) =4a(3) =9a(4) =21a(5) =100a(6) =400a(7) =561a(8) =900a(9) =2100a(10) =8821a(11) =10000a(12) =11221a(13) =17821a(14) =40000a(15) =56100a(16) =73221a(17) =90000a(18) =210000a(19) =211201a(20) =518041a(21) =882100a(22) =1000000a(23) =1001614a(24) =1002621a(25) =1012021a(26) =1012224a(27) =1122100a(28) =1302801a(29) =1782100