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 A261130 #31 Sep 07 2022 15:49:18 %S A261130 1,2,3,5,35,7,77,143,143,2431,46189,4199,96577,7429,7429,215441, %T A261130 6678671,392863,392863,765049,765049,31367009,1348781387,58642669, %U A261130 2756205443,2756205443,2756205443,146078888479,146078888479,5037203051,297194980009,584803025179 %N A261130 a(n) = Product(p prime | n < p <= 2*n). %C A261130 Essentially the same as A068111. - _R. J. Mathar_, Nov 23 2015 %C A261130 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 %e A261130 a(0) = 1 because the empty product is 1 by convention. %e A261130 a(4) = 35 because {p prime | 4 < p <= 8} = {5, 7}. %p A261130 a := n -> convert(select(isprime, {$n+1..2*n}),`*`): %p A261130 print(seq(a(n), n=0..31)); %t A261130 Join[{1},Table[Times@@Prime[Range[PrimePi[n]+1,PrimePi[2n]]],{n,40}]] (* _Harvey P. Dale_, May 09 2017 *) %o A261130 (PARI) A261130(n,P=1)={forprime(p=n+1,2*n,P*=p);P} \\ _M. F. Hasler_, Nov 25 2015 %o A261130 (Python) %o A261130 from sympy import primorial %o A261130 def A261130(n): return primorial(n<<1,nth=False)//primorial(n,nth=False) if n else 1 # _Chai Wah Wu_, Sep 07 2022 %Y A261130 Cf. A000984 (binomial(2*n,n)), A034386, A263931, A356637. %K A261130 nonn,easy %O A261130 0,2 %A A261130 _Peter Luschny_, Oct 31 2015