

A081768


Number of k, 1<=k<=n, such that C(n,k) divides C(2n,2k).


1



1, 2, 3, 3, 5, 5, 3, 7, 7, 5, 7, 5, 7, 11, 9, 3, 5, 13, 9, 13, 7, 3, 11, 9, 7, 9, 7, 11, 11, 9, 3, 9, 23, 13, 19, 9, 3, 7, 11, 7, 11, 9, 9, 9, 7, 7, 5, 19, 13, 23, 15, 7, 17, 13, 9, 7, 5, 5, 7, 11, 11, 11, 19, 11, 15, 9, 11, 21, 19, 11, 9, 9, 9, 13, 11, 5, 13, 21, 9, 11, 15, 7, 13, 9, 7, 11, 7, 15
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OFFSET

1,2


COMMENTS

Is a(n) odd for n>2 ? All odd numbers occur? Does equation a(x)=2m+1 have infinitely many solutions for any m>=1?


LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000


MATHEMATICA

Total/@Table[If[Divisible[Binomial[2n, 2k], Binomial[n, k]], 1, 0], {n, 90}, {k, n}] (* Harvey P. Dale, Jul 10 2012 *)


CROSSREFS

Sequence in context: A265145 A103310 A046146 * A273493 A193404 A072923
Adjacent sequences: A081765 A081766 A081767 * A081769 A081770 A081771


KEYWORD

easy,nonn


AUTHOR

Benoit Cloitre, Apr 09 2003


STATUS

approved



