This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A080384 #26 Mar 05 2023 16:27:32 %S A080384 5,7,9,11,15,17,19,21,23,27,29,33,35,39,43,45,47,49,51,53,55,59,61,63, %T A080384 65,67,69,71,73,75,77,79,81,83,87,89,93,95,97,99,101,103,105,107,109, %U A080384 111,113,115,117,119,121,123,125,127,129,131,135,137,139,141,143,145 %N A080384 Numbers k such that there are exactly 6 numbers j for which binomial(k, floor(k/2)) / binomial(k,j) is an integer, i.e., A080383(k) = 6. %H A080384 Vaclav Kotesovec, <a href="/A080384/b080384.txt">Table of n, a(n) for n = 1..44084</a> %e A080384 For n=9, the central binomial coefficient (C(9,4) = 126) is divisible by C(9,0), C(9,1), C(9,4), C(9,5), C(9,8), and C(9,9); certain primes are missing, certain composites are here. %t A080384 Position[Table[Count[Binomial[n,Floor[n/2]]/Binomial[n,Range[0,n]],_?IntegerQ],{n,150}],6]//Flatten (* _Harvey P. Dale_, Mar 05 2023 *) %o A080384 (PARI) isok(n) = my(b=binomial(n, n\2)); sum(i=0, n, (b % binomial(n, i)) == 0) == 6; \\ _Michel Marcus_, Jul 29 2017 %Y A080384 Cf. A327430, A080385, A080386, A327431, A080387. %Y A080384 Cf. A001405, A057977. %K A080384 nonn %O A080384 1,1 %A A080384 _Labos Elemer_, Mar 12 2003