No. 600 - A regular polyomino , an hexomino (with all 35 pieces that can be constructed of 6 squares)
in a rectangular tray with a very small protuberance.
It's very peculiar these pieces won't fit in any rectangular surface (like 14 x 15 = 210).
Golomb proved this in a simple and understandable way in his book.
Only one puzzle of the serie is more difficult than this one. Still Tenyo claims the existance of over 1.000.000.000 (!) different solutions! That is the largest number in this serie! With some tricks I found myself over 10.000.000 solutions by hand.
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