%I A074143
%S A074143 1,2,9,48,300,2160,17640,161280,1632960,18144000,219542400,2874009600,
%T A074143 40475635200,610248038400,9807557760000,167382319104000,
%U A074143 3023343138816000,57621363351552000,1155628453883904000
%N A074143 a(1) = 1; a(n) = n * sum {a(k) | k < n}.
%H A074143 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas 
               for Some Functions on Finite Sets</a>
%F A074143 a(n) = n^2*a(n-1)/(n-1) for n > 2.
%F A074143 a(n) = n*ceiling[n!/2] = n*A001710(n-1) = A001710(n+1)-A001710(n) = ceiling[A001563(n)/
               2] - Henry Bottomley (se16(AT)btinternet.com), Nov 27 2002
%p A074143 seq(sum(mul(j,j=3..n), k=1..n), n=1..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), 
               Jun 01 2007
%Y A074143 Sequence in context: A153390 A118341 A100427 this_sequence A052826 A115599 
               A000167
%Y A074143 Adjacent sequences: A074140 A074141 A074142 this_sequence A074144 A074145 
               A074146
%K A074143 nonn
%O A074143 1,2
%A A074143 Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 28 2002
%E A074143 More terms from Henry Bottomley (se16(AT)btinternet.com), Nov 27 2002