Numbers k such that k^2 is a square arising in A154138.

Terms

a(0) =2a(1) =3a(2) =9a(3) =16a(4) =52a(5) =93a(6) =303a(7) =542a(8) =1766a(9) =3159a(10) =10293a(11) =18412a(12) =59992a(13) =107313a(14) =349659a(15) =625466a(16) =2037962a(17) =3645483a(18) =11878113a(19) =21247432a(20) =69230716a(21) =123839109a(22) =403506183a(23) =721787222a(24) =2351806382a(25) =4206884223a(26) =13707332109a(27) =24519518116a(28) =79892186272