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Search: id:A054780
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| A054780 |
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Number of n-covers of a labeled n-set. |
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+0
3
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| 1, 1, 3, 32, 1225, 155106, 63602770, 85538516963, 386246934638991, 6001601072676524540, 327951891446717800997416, 64149416776011080449232990868, 45546527789182522411309599498741023
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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a(n)=sum_{k=0..n} (-1)^k*C(n, k)*C(2^(n-k)-1, n).
Also a(n) = (1/n!)*sum_{k=0..n} Stirling1(n+1, k+1)*(2^k-1)^n.
G.f.: Sum_{n>=0} ln(1+(2^n-1)*x)^n/((1+(2^n-1)*x)*n!). - Paul Hanna and Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 16 2008
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CROSSREFS
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Cf. A048291.
Main diagonal of A055154.
Sequence in context: A123336 A058479 A129431 this_sequence A134474 A096469 A106423
Adjacent sequences: A054777 A054778 A054779 this_sequence A054781 A054782 A054783
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), May 21 2000
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