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 A232618 #15 May 03 2021 15:36:51
%S A232618 0,2,3,69,60,4500,104580,186795,13497435,442245825,13003053525,
%T A232618 64585694250,3576632909850,147580842959550,5708173568847750,
%U A232618 27904470362393625,2292043480058957625,126842184377462428875,6371504674680470700375,312265748715684068930625
%N A232618 a(n) = (2n)!! mod (2n-1)!! where k!! = A006882(k).
%C A232618 (2n)!! is the product of first n even numbers, (2n-1)!! is the product of first n odd numbers.
%F A232618 a(n) = A006882(2*n) mod A006882(2*n-1).
%e A232618 a(3) = A006882(6) mod A006882(5) = 2*4*6 mod 1*3*5 = 48 mod 15 = 3.
%t A232618 Table[Mod[(2n)!!,(2n-1)!!],{n,20}] (* _Harvey P. Dale_, Sep 23 2020 *)
%o A232618 (Python)
%o A232618 o=e=1
%o A232618 for n in range(1,99,2):
%o A232618 o*=n
%o A232618 e*=n+1
%o A232618 print(str(e%o), end=',')
%Y A232618 Cf. A006882, A122649, A129890, A232617.
%K A232618 nonn
%O A232618 1,2
%A A232618 _Alex Ratushnyak_, Nov 27 2013