a(1) = 1; a(n) is the smallest square > a(n-1) which differs from it at every digit.

Terms

a(0) =1a(1) =4a(2) =9a(3) =16a(4) =25a(5) =36a(6) =49a(7) =64a(8) =81a(9) =100a(10) =225a(11) =361a(12) =400a(13) =529a(14) =676a(15) =729a(16) =841a(17) =900a(18) =1024a(19) =2116a(20) =3025a(21) =4356a(22) =5041a(23) =6400a(24) =7056a(25) =8100a(26) =9025a(27) =10201a(28) =21025a(29) =30276