24/07/17 13:57:52.29 HIM317T1.net
>7の想定解
fn[n_] = (n^4+2n^3+2n^2+n+1)(n^2+n+1)(n+1)n
検証
In[2]:= Table[fn[n],{n,1,50}]
Out[2]= {42, 1806, 24492, 176820, 865830, 3263442, 10192056, 27630792, 67084290, 149096310, 308230692,
> 599882556, 1109322942, 1963420410, 3345523440, 5514027792, 8825193306, 13760814942, 20961393180,
> 31265489220, 45755990742, 65814054306, 93181530792, 130032720600, 179056345650, 243548665542,
> 327518705556, 435806604492, 574216130670, 749662454730, 970336308192, 1245885697056,
> 1587616380042, 2008712361390, 2524477688460, 3152600884692, 3913443388806, 4830353411442,
> 5930006660760, 7242775428840, 8803127571042, 10650056950806, 12827546962692, 15385068786780,
> 18378116067870, 21868777753242, 25926350863056, 30627995007792, 36059430507450, 42315682007550}