$ g++ a30.cpp; a.exe
srand=1141664878
---- N=9
1,2,16.009400
1,3,16.731600
1,4,16.800250
1,6,16.825450
2,4,16.865200
2,5,16.961100
2,6,16.985000
---- N=10
1,2,17.405650
1,3,18.238400
1,4,18.388900
1,7,18.413050
2,4,18.433550
2,5,18.520400
2,7,18.524750
5,8,18.535600
---- N=11
1,2,18.844300
1,3,19.736950
1,4,19.907300
2,4,19.992550
2,5,20.199100
2,7,20.212700
---- N=12
1,2,20.126450
1,3,21.130750
1,4,21.409450
1,5,21.455700
2,4,21.498000
2,5,21.716250
2,9,21.742050
3,5,21.759950
5,8,21.779450
---- N=13
1,2,21.465000
1,3,22.599050
1,4,22.905050
1,5,22.961350
2,4,22.984750
2,5,23.266900
2,6,23.286800
3,7,23.303950
4,6,23.305800
6,9,23.311400
7,9,23.318300
---- N=14
1,2,22.738150
1,3,24.018150
1,4,24.347000
1,5,24.380100
1,6,24.410200
2,4,24.413400
2,5,24.770950
2,6,24.779750
2,10,24.803950
3,9,24.852800
---- N=15
1,2,24.118700
1,3,25.456750
1,4,25.802600
1,5,25.809700
1,6,25.838350
1,11,25.862000
2,5,26.276550
2,6,26.297450
2,7,26.314900
3,8,26.331350
5,8,26.383500
---- N=16
1,2,25.374600
1,3,26.777650
1,4,27.138550
1,5,27.232500
1,10,27.281050
2,5,27.689600
2,6,27.739250
2,7,27.774950
2,12,27.781450
3,7,27.819550
3,10,27.833300
7,11,27.836250
---- N=17
1,2,26.575900
1,3,28.165350
1,4,28.525850
1,5,28.671450
1,7,28.714450
2,5,29.114150
2,6,29.228900
2,13,29.238950
3,9,29.295550
---- N=18
1,2,27.829800
1,3,29.533850
1,4,29.930150
1,5,30.046000
1,6,30.049050
1,13,30.090550
2,5,30.527250
2,6,30.628800
2,7,30.687550
4,10,30.703500
6,10,30.719850
6,14,30.725250