Search: id:A138265
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%I A138265
%S A138265 1,1,1,2,5,16,61,271,1372,7795,49093,339386,2554596,20794982,182010945,
%T A138265 1704439030,17003262470,180011279335,2015683264820,23801055350435,
%U A138265 295563725628564,3850618520827590,52514066450469255
%N A138265 Number of upper triangular zero-one matrices with n ones and no zero 
               rows or columns.
%F A138265 G.f.: Sum(Product(1-1/(1+x)^i,i=1..n),n=0..infinity).
%F A138265 a(n) = (1/n!)*Sum_{k=0..n} Stirling1(n,k)*A079144(k). a(n) = Sum_{k=0..n} 
               (-1)^(n-k)*binomial(n-1,k-1)*A022493(k).
%p A138265 g:=sum(product(1-1/(1+x)^i,i=1..n),n=0..35): gser:=series(g,x=0,30): 
               seq(coeff(gser,x,n),n=0..22); - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               Mar 23 2008
%Y A138265 Cf. A005321, A104602, A135588.
%Y A138265 Sequence in context: A012159 A009736 A104858 this_sequence A000111 A163747 
               A007976
%Y A138265 Adjacent sequences: A138262 A138263 A138264 this_sequence A138266 A138267 
               A138268
%K A138265 easy,nonn
%O A138265 0,4
%A A138265 Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 10 2008, Mar 11 2008
%E A138265 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 23 2008

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