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[Math]

1. Number of digits in a number ~ log(x) + 1
2. Number of digits in factorial n! = log(n) + log(n-1) + ... + log(1) + 1 (log base 10 in C is log10(double).
3. (n choose k) = product (i = 1 to k) {(n - k + i) / i} (530 - Binomial showdown)
4. (n choose k) = (n choose n-k) (530 - Binomial showdown)

[R] 

1. Uninstall R Completely from your Mac OS X

[Linear Algebra]


[Python]