Numbers k such that the concatenation of 8*k with k gives a square.

Terms

a(0) =1a(1) =4a(2) =9a(3) =89a(4) =889a(5) =8889a(6) =88889a(7) =888889a(8) =8888889a(9) =88888889a(10) =888888889a(11) =1026765584a(12) =1066636289a(13) =1107266436a(14) =1148656025a(15) =1190805056a(16) =1233713529a(17) =1277381444a(18) =1321808801a(19) =1366995600a(20) =1412941841a(21) =1459647524a(22) =1507112649a(23) =1555337216