When squared gives number composed of digits {2,5,6}.

Terms

a(0) =5a(1) =15a(2) =16a(3) =25a(4) =75a(5) =235a(6) =475a(7) =515a(8) =516a(9) =725a(10) =5125a(11) =7525a(12) =22925a(13) =23585a(14) =72475a(15) =505525a(16) =515415a(17) =2501125a(18) =15008516a(19) =23711235a(20) =72267325a(21) =149081275a(22) =250133275a(23) =256032335a(24) =505228925a(25) =2294919525a(26) =5153315075a(27) =15040686675a(28) =50222133125