To see "I"- or "+"- based breakdowns, click on the P-pentominoes:
(some placements have unique solutions !)
the 2339 solutions of the 6x10
the 1010 solutions of the 5x12
the 368 solutions of the 4x15
congruent halves of the 6x10's
to refresh the sample solutions
of all four standard size puzzles.