N = 2: an Octomino:

N = 3: a 10omino:

N = 4: an hexomino (I think there are 3 different):

N = 5: a 9omino: by Erich Friedman

N = 6: a 9omino:

N = 7: a 7omino: by Erich Friedman

N = 8: a 6omino: by Erich Friedman

N = 9: a 7omino: by Erich Friedman

N >= 10: a 6omino: by Erich Friedman:  
Example, N = 11: 
N  2  3  4  5  6  7  8  9  > 
Pieces  8  10  6  9  9  7  6  7  6 
N = 2: an Octomino:

N = 3: a 10omino:

N = 4: a 11omino:

N = 5: a 12omino: by Junk Kato

N = 6: a 11omino:

N = 7: a 11omino: by Junk Kato

N = 8: a 10omino:

N = 9: a 11omino:

N = 10: a 21omino: by Erich Friedman

N  2  3  4  5  6  7  8  9  > 
Pieces  8  10  11  12  11  11  10  11  3n9 
Rodolfo Marcelo Kurchan / Lavalle 3340 21"3" / (1190) Buenos Aires  Argentina
eMail: rodolfo@kurchan.com.ar
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