Timeline for Pascal triangle and prime numbers
Current License: CC BY-SA 2.5
3 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 15, 2010 at 18:21 | comment | added | Douglas Zare | Your K(X,p) is also (X - (sum of the digits of X base p))/(p-1). So, the number of times p divides M choose N is the number of carries you perform when you add N to M-N base p. That makes it clear how many entries of the Mth row of Pascal's triangle are not divisible by p, and which ones. | |
| Dec 17, 2009 at 18:11 | comment | added | Harrison Brown | Definitely not original, but definitely fun, and closely related to my answer. The different thing with composite numbers is that your solution depends on the equation: (# of times p divides a/b) = (# of times p divides a) - (# of times p divides b), which is true when p is prime but not if p is composite. (Again, take p = 10, a = 1000, b = 250.) | |
| Dec 17, 2009 at 17:52 | history | answered | Dan | CC BY-SA 2.5 |