OFFSET
0,2
COMMENTS
The numerators are given in A056616.
LINKS
Michel Marcus, Table of n, a(n) for n = 0..2000
FORMULA
a(n) = denominator(r(n)) with r(n) = binomial(2*n,n)/(2*n+1).
G.f. of r(n): 1/(2*sqrt(x))*arcsin(2*sqrt(x)). [Vladimir Kruchinin, May 31 2013]
EXAMPLE
The rationals r(n) begin: 1, 2/3, 6/5, 20/7, 70/9, 252/11, 924/13, 1144/5, 12870/17, ...
MATHEMATICA
Table[Binomial[2 n, n]/(2 n + 1), {n, 0, 70}]//Denominator (* Harvey P. Dale, May 01 2019 *)
PROG
(Magma) [Denominator((Binomial (2*n, n)) / (2*n + 1)): n in [0..70]]; // Vincenzo Librandi, May 27 2019
(PARI) a(n) = denominator(binomial(2*n, n) / (2*n+1)); \\ Michel Marcus, May 27 2019
CROSSREFS
KEYWORD
nonn,easy,frac
AUTHOR
N. J. A. Sloane, Aug 28 2000
STATUS
approved