11
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Is there a solution for a straight-bar piece not touching the edge of the rectangle? By rectangle solution, I mean either one of the patterns 15x4, 12x5, or 10x6. By straight-bar piece, I mean the piece of 5 stones in a straight row. Literate pentomino crackers denote this piece with the letter "I".

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1 Answer 1

12
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Here's one solution for the $10{\times}6$ rectangle:

enter image description here

Here are all $11$:

vvvllllzzy
viiiiilzyy
vxffwwzzny
xxxffwwtny
uxufppwtnn
uuuppptttn

vvvllllzzn
viiiiilznn
vxffwwzzny
xxxffwwtny
uxufppwtyy
uuupppttty

yzzllllvvv
yyzliiiiiv
ynzzwwxffv
yntwwxxxff
nntwppxufu
ntttpppuuu

nzzllllvvv
nnzliiiiiv
ynzzwwxffv
yntwwxxxff
yytwppxufu
ytttpppuuu

tnnnllllpp
tttnnfflpp
tiiiiiffxp
vvvzwwfxxx
vzzzywwuxu
vzyyyywuuu

wwtttxffuu
pwwtxxxffu
ppwtyxzfuu
ppyyyyzzzv
liiiiinnzv
llllnnnvvv

pptttxffuu
ppwtxxxffu
pwwtyxzfuu
wwyyyyzzzv
liiiiinnzv
llllnnnvvv

wwfftttxuu
pwwfftxxxu
ppwfytzxuu
ppyyyyzzzv
liiiiinnzv
llllnnnvvv

ppfftttxuu
ppwfftxxxu
pwwfytzxuu
wwyyyyzzzv
liiiiinnzv
llllnnnvvv

uuxfftttpp
uxxxfftwpp
uuxzfytwwp
vzzzyyyyww
vznniiiiil
vvvnnnllll

uuxfftttww
uxxxfftwwp
uuxzfytwpp
vzzzyyyypp
vznniiiiil
vvvnnnllll

There is only one solution for the $12{\times}5$ rectangle:

enter image description here

llllnnnffppp
liiiiinnffpp
vzyyyywtfxuu
vzzzywwtxxxu
vvvzwwtttxuu

There are no solutions for the $15{\times}4$ rectangle.

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1
  • $\begingroup$ The 11 solutions for 10x6 can be grouped into 3 classes: the first four are generated by flipping NY and/or FX from one of them, the 5th is unique, and the other 6 are generated by flipping WP and/or permuting XFT. $\endgroup$
    – Bubbler
    Commented Jul 8 at 1:23

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