A143357 - OEIS

%I #11 Nov 07 2023 11:17:56

%S 0,0,0,0,0,2,12,70,448,3298,27490,255876,2631876,29652480,363242880,

%T 4807626352,68375130352,1040021719578,16848351857178,289631191449600,

%U 5266021662720000,100970241446066086,2036233202495666086,43086694564808294400,954536002666522214400,22095740802465792000000

%N Floor((n-1)!/[n(n+1)]).

%C All terms are even.

%D T. Andreescu, D. Andrica and Z. Feng, 104 Number Theory Problems (from the training of the USA IMO team), Birkhäuser, Boston, 2007, Introductory problem # 50, pp. 82,126,127.

%p seq(floor(factorial(n-1)/(n*(n+1))),n=1..25);

%t Table[Floor[(n-1)!/(n(n+1))],{n,30}] (* _Harvey P. Dale_, Apr 11 2012 *)

%K nonn

%O 1,6

%A _Emeric Deutsch_, Aug 11 2008