A080391 Number of integers among the following n+1 quotients: A001405(n)/A001405(k), k=0,..,n. Number of values k for which the n-th central binomial coefficient[cbc] is divisible by the k-th cbc-s k=0,..n.

1, 2, 3, 3, 5, 4, 5, 3, 6, 6, 7, 6, 7, 6, 7, 4, 8, 5, 7, 4, 5, 6, 7, 4, 5, 8, 9, 8, 9, 8, 9, 4, 8, 7, 9, 10, 13, 12, 13, 13, 18, 9, 11, 8, 9, 8, 9, 7, 9, 8, 9, 8, 9, 4, 5, 8, 9, 12, 13, 4, 5, 4, 5, 4, 9, 9, 12, 9, 11, 8, 9, 4, 5, 4, 5, 10, 11, 8, 9, 7, 9, 14, 15, 14, 15, 14, 15, 12, 13, 12, 13, 12, 13

Offset

0,2

Links

Table of n, a(n) for n=0..92.

Example

n=11: the 12 relevant C(11,5)/C(k,floor(k/2)) quotients are {462,462,231,154,77,231/5,231/10,66/5,33/5,11/3,11/6,1}; of which a(12)=6 are integers.

Mathematica

Table[Count[Table[IntegerQ[Binomial[n, Floor[n/2]]/ Binomial[i, Floor[i/2]]], {i, 0, n}], True], {n, 1, 256}]

Crossrefs

Cf. A001405.

Sequence in context: A354940 A210874 A244796 * A273494 A116922 A086898

Adjacent sequences: A080388 A080389 A080390 * A080392 A080393 A080394

Keyword

nonn

Author

Labos Elemer, Mar 13 2003

Status

approved