%I #5 Jun 29 2013 12:15:13

%S 1,16,196,1936,19881,199809,1999396,19998784,199996164,1999967841,

%T 19999899241,199999467369,1999998409369,19999991458225,

%U 199999982358225,1999999950806881,19999999932878736,199999999552824025

%N Largest perfect square less than 2*10^n.

%F a(n) = floor(sqrt(2*10^n))^2.

%e a(4) = 19881 because 19881 is the largest perfect square less than 2*10^4.

%t Table[Floor[Sqrt[2*10^k]]^2,{k,0,30}]

%K easy,nonn

%O 0,2

%A Adam M. Kalman (akalman(AT)icsd.k12.ny.us), Mar 21 2007