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A007537
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Number of proper covers of an n-set.
(Formerly M5287)
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6
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0, 1, 45, 15913, 1073579193, 4611686005542975085, 85070591730234615801280047645054636261, 28948022309329048855892746252171976961956366698726387156269151989162886489297
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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REFERENCES
| A. J. Macula, Covers of a finite set, Math. Mag., 67 (1994), 141-144.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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MAPLE
| A007537 := proc(n) 1/2*sum((-1)^k*binomial(n, k)*2^(2^(n-k)), k=0..n)-2^(2^n)/4 end;
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MATHEMATICA
| Table[1/2 Sum[(-1)^k Binomial[n, k]2^(2^(n-k)), {k, 0, n}]-2^2^n/4, {n, 8}] (* From Harvey P. Dale, Oct 31 2011 *)
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CROSSREFS
| Cf. A003465.
Sequence in context: A201004 A171118 A199521 * A125113 A003739 A145319
Adjacent sequences: A007534 A007535 A007536 * A007538 A007539 A007540
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KEYWORD
| nonn,easy,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
| One more term from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 01 2005
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