Search: id:A035348
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%I A035348
%S A035348 1,1,1,1,6,1,1,25,22,1,1,90,305,65,1,1,301,3410,2540,171,1,1,966,
%T A035348 33621,77350,17066,420,1,1,3025,305382,2022951,1298346,100814,988,1,
%U A035348 1,9330,2619625,47708115,83384427,18151560,549102,2259,1
%N A035348 Triangle of a(n,k) = number of k-member minimal covers of an n-set (n 
               >= 1, k >= 1).
%C A035348 These are what Clarke calls "Minimal disordered k-covers of labeled n-set".
%D A035348 R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
%D A035348 Hearne and Wagner, Minimal covers of finite sets, Discr. Math. 5 (1973), 
               247-251.
%H A035348 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               MinimalCover.html">Link to a section of The World of Mathematics.</
               a>
%F A035348 E.g.f.: Sum((exp(y)-1)^n*exp(y*(2^n-n-1))*x^n/n!, n=0..infinity). - Vladeta 
               Jovovic (vladeta(AT)eunet.rs), May 08 2004
%e A035348 1; 1,1; 1,6,1; 1,25,22,1; ...
%o A035348 (PARI) C(n,k) = if(k<0|k>n,0,n!/k!/(n-k)!); a(n,k)=sum(i=0,k, (-1)^i*C(k,
               i)*(2^k-1-i)^n)/k!; printp(matrix(10,10,n,k,a(n-1,k-1)))
%Y A035348 Row sums are A046165. Cf. A049055, A003465, A002177.
%Y A035348 Sequence in context: A060187 A156139 A155863 this_sequence A140945 A141688 
               A166960
%Y A035348 Adjacent sequences: A035345 A035346 A035347 this_sequence A035349 A035350 
               A035351
%K A035348 nonn,tabl,easy,nice
%O A035348 1,5
%A A035348 N. J. A. Sloane (njas(AT)research.att.com).
%E A035348 Entry improved by Michael Somos

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