a(1) = 4; a(n) = least number such that the concatenation a(n)a(n-1)...a(2)a(1) is a square.

A061361

a(1) = 4; a(n) = least number such that the concatenation a(n)a(n-1)...a(2)a(1) is a square.

Terms

    a(0) =4a(1) =6a(2) =17a(3) =604a(4) =9612a(5) =85848855

External references