4 things taken 2 at a time is 6 exactly.
10 things taken 5 at a time is 252 exactly.
49 things taken 6 at a time is 13983816 exactly.
2000000000 things taken 0 at a time is 1 exactly.
2000000000 things taken 1 at a time is 2000000000 exactly.
2000000000 things taken 1999999999 at a time is 2000000000 exactly.
2000000000 things taken 2000000000 at a time is 1 exactly.
65000 things taken 2 at a time is 2112467500 exactly.
65000 things taken 64998 at a time is 2112467500 exactly.
64999 things taken 2 at a time is 2112402501 exactly.
64999 things taken 64997 at a time is 2112402501 exactly.
2300 things taken 3 at a time is 2025189100 exactly.
2300 things taken 2297 at a time is 2025189100 exactly.
400 things taken 4 at a time is 1050739900 exactly.
100 things taken 5 at a time is 75287520 exactly.
100 things taken 6 at a time is 1192052400 exactly.
70 things taken 7 at a time is 1198774720 exactly.
50 things taken 8 at a time is 536878650 exactly.
40 things taken 9 at a time is 273438880 exactly.
40 things taken 10 at a time is 847660528 exactly.
33 things taken 11 at a time is 193536720 exactly.
33 things taken 12 at a time is 354817320 exactly.
33 things taken 13 at a time is 573166440 exactly.
33 things taken 14 at a time is 818809200 exactly.
33 things taken 15 at a time is 1037158320 exactly.
33 things taken 16 at a time is 1166803110 exactly.
