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%I #14 Jun 01 2019 15:58:10
%S 1,2,4,12,48,80,360,1344,2688,8640,51840,63360,443520,1198080,2515968,
%T 10886400,48384000,87736320,465315840,1134673920,3309465600,
%U 11887948800,71530905600,78343372800,528817766400,1839366144000,3260694528000,15837659136000,82169502105600
%N a(n) = Product_{k=1..n} floor((2*n+1)/k - 1).
%C Forms the right border of odd-indexed rows in irregular triangle A207645.
%H Paul D. Hanna, <a href="/A207647/b207647.txt">Table of n, a(n) for n = 0..500</a>
%F a(n) = A207645(2*n+1, n).
%e Illustration of the initial terms:
%e a(1) = [3/1-1] = 2;
%e a(2) = [5/1-1]*[5/2-1] = 4;
%e a(3) = [7/1-1]*[7/2-1]*[7/3-1] = 12;
%e a(4) = [9/1-1]*[9/2-1]*[9/3-1]*[9/4-1] = 48;
%e a(5) = [11/1-1]*[11/2-1]*[11/3-1]*[11/4-1]*[11/5-1] = 80; ...
%e where [x] = floor(x).
%t Table[Product[Floor[(2n+1)/k-1],{k,n}],{n,0,30}] (* _Harvey P. Dale_, Jun 01 2019 *)
%o (PARI) {a(n)=prod(k=1,n,floor((2*n+1)/k-1))}
%o for(n=0,50,print1(a(n),", "))
%Y Cf. A207645, A207646, A207643, A207644.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Feb 20 2012
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