Koblitz curves

Elliptic curve defined over F2 on the form
Y^2 + XY = X^3 + aX^2 +1, with a 1 or 0. Koblitz idea: define the curve in F2, but take points on E with coordinates i F2^k.
An easy way to calculate the order of the curve - i.e. the number of points on E(F2^k) (with a=0) is
#E(F2^k) = 2^k + 1 - ((-1+sqrt(-7))/2)^k - ((-1-sqrt(-7))/2)^k

for k=11
we have a cute tiny one with order 2116

for k=97
it's a little larger:
158456325028528296935114828764

for k=163
the number of points is:
11692013098647223345629473816263631617836683539492

for k=233
the number of points is:
13803492693581127574869511724554051042283763955449008505312348098965372

for k= 283
the number of points is:
15541351137805832567355695254588151253139246935172245297183499990119263\
318817690415492

k=409 gives:
13221119375804971979038306160655420796568093659285624385692975800915228\
45156996764202693033831109832056385466362470925434684

k=571 gives:
7729075046034516689390703781863974688597854659412869997314470502903038\
2845791208490725359140908268473388268512033014058450946998962664692477\
18729686468370014222934741106692

isn't that amazing?