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 A095987 #17 Feb 10 2025 08:46:06
%S A095987 1,1,1,1,1,1,3,3,3,3,15,15,45,45,315,315,315,315,2835,2835,14175,
%T A095987 14175,155925,155925,467775,467775,6081075,6081075,42567525,42567525,
%U A095987 638512875,638512875,638512875,638512875,10854718875,10854718875,97692469875,97692469875
%N A095987 a(n) = gcd(n!!, (n-1)!!) where n!! = A006882.
%C A095987 Let f_n(m) be a multifactorial: for m = positive integer, f_n(m) = Product_{k=0..floor((m-1)/n)} (m - k*n). E.g., f_2(m) = m!!. f_n(0) is defined as 1.
%F A095987 a(2m) = a(2m+1) = A049606(m).
%p A095987 a:= n-> (d-> gcd(d(n), d(n-1)))(doublefactorial):
%p A095987 seq(a(n), n=0..40); # _Alois P. Heinz_, Oct 26 2019
%t A095987 f[n_] := GCD[n!!, (n - 1)!! ]; Table[ f[n], {n, 35}]
%t A095987 GCD@@#&/@Partition[Range[0,40]!!,2,1] (* _Harvey P. Dale_, May 04 2015 *)
%Y A095987 a(2n) gives A049606.
%K A095987 nonn
%O A095987 0,7
%A A095987 _Leroy Quet_, Jul 18 2004
%E A095987 Edited and extended by _Robert G. Wilson v_, Jul 19 2004
%E A095987 Missing a(0)=1 inserted by _Alois P. Heinz_, Oct 26 2019