Help with a summation

Revision en3, by MedoN11, 2017-06-19 04:29:43


Recently, I was solving a problem to which I simplified it to evaluating this summation:

C is n choose k. N is up to 1000, and K is up to 2^30.

Answer appears to be I guess {K * (N - 1)K}

I can't get however how to arrive at this, or perhaps compute the original summation in a smart way, I tried messing expanding nCk to factorials, but didn't get anywhere. <.<


  Rev. Lang. By When Δ Comment
en3 English MedoN11 2017-06-19 04:29:43 2 Tiny change: 'i}*(N-1)^{k - i}*{C(K' -> 'i}*(N-1)^{K - i}*{C(K'
en2 English MedoN11 2017-06-19 04:28:58 20 Tiny change: 's compute it in a smar' -> 's compute the original summation in a smar'
en1 English MedoN11 2017-06-19 04:27:52 440 Initial revision (published)