No.1 D
17=7+10 23=11+12 so 31=17+14
No.2 B
(2*n-1)*(3*n-1)
No.3 D
1=1*1*1-2 4=2*2*2-4 21=3*3*3-6 56=4*4*4-8 115=5*5*5-10 204=6*6*6-12
n^3-2*n
No.1 D
17=7+10 23=11+12 so 31=17+14
No.2 B
(2*n-1)*(3*n-1)
No.3 D
1=1*1*1-2 4=2*2*2-4 21=3*3*3-6 56=4*4*4-8 115=5*5*5-10 204=6*6*6-12
n^3-2*n