OFFSET
0,2
COMMENTS
Essentially the same as A068111. - R. J. Mathar, Nov 23 2015
a(n) is a divisor of binomial(2*n, n); the quotient binomial(2*n, n) / a(n) is A263931(n). - Robert FERREOL, Sep 03 2022
EXAMPLE
a(0) = 1 because the empty product is 1 by convention.
a(4) = 35 because {p prime | 4 < p <= 8} = {5, 7}.
MAPLE
a := n -> convert(select(isprime, {$n+1..2*n}), `*`):
print(seq(a(n), n=0..31));
MATHEMATICA
Join[{1}, Table[Times@@Prime[Range[PrimePi[n]+1, PrimePi[2n]]], {n, 40}]] (* Harvey P. Dale, May 09 2017 *)
PROG
(PARI) A261130(n, P=1)={forprime(p=n+1, 2*n, P*=p); P} \\ M. F. Hasler, Nov 25 2015
(Python)
from sympy import primorial
def A261130(n): return primorial(n<<1, nth=False)//primorial(n, nth=False) if n else 1 # Chai Wah Wu, Sep 07 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Peter Luschny, Oct 31 2015
STATUS
approved