No. 6 - is a real regular polyomino, an hexiamond (all 12 possible pieces made of 6 triangles) in an onion-shape tray.
Tenyo claims there exist over 5000 solutions.
I discovered over 600 solutions with my bare hands, but my solver found 5885.
It's less simple than it looks, it always took me quite some time to find a new solution.
Tenyo no #6 (from a different series)
You can download my Hexiamond solver (written in Delphi 6 for Windows) here.
The solver can show all solutions of the puzzles above.
Free Hexiamond solver
More hexiamonds .
more Beat The Computer puzzles
More about Polyominos