A080387 - OEIS

A080387

Numbers k such that there are exactly 10 numbers j for which binomial(k, floor(k/2)) / binomial(k,j) is an integer, i.e., A080383(k) = 10.

%I #18 Sep 10 2019 03:03:14

%S 13,31,41,57,85,91,133,155,177,183,209,221,253,281,307,313,341,375,

%T 381,409,419,441,457,463,477,481,533,553,599,617,625,631,645,651,661,

%U 691,737,757,829,841,859,871,881,885,901,919,929,937,953,967,987,993

%N Numbers k such that there are exactly 10 numbers j for which binomial(k, floor(k/2)) / binomial(k,j) is an integer, i.e., A080383(k) = 10.

%H Vaclav Kotesovec, <a href="/A080387/b080387.txt">Table of n, a(n) for n = 1..5113</a>

%e For n=13, the central binomial coefficient (C(13,6) = 1716) is divisible by 10 binomial coefficients C(13,j); the 4 nondivisible cases are C(13,4), C(13,5), C(13,8), and C(13,9).

%Y Cf. A327430, A080384, A080385, A080386, A327431.

%Y Cf. A001405, A057977.

%K nonn

%O 1,1

%A _Labos Elemer_, Mar 12 2003