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Search: id:A005744
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| A005744 |
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G.f.: x*(1+x-x^2)/((1-x)^4*(1+x)).
(Formerly M3360)
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+0
9
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| 0, 1, 4, 9, 17, 28, 43, 62, 86, 115, 150, 191, 239, 294, 357, 428, 508, 597, 696, 805, 925, 1056, 1199, 1354, 1522, 1703, 1898, 2107, 2331, 2570, 2825, 3096, 3384, 3689, 4012, 4353, 4713, 5092, 5491, 5910, 6350, 6811, 7294, 7799, 8327, 8878, 9453, 10052
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Number of n-covers of a 2-set.
a(n)=A002623(n)-(n+1).
Boolean switching functions a(n,s) for s = 2.
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REFERENCES
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R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
Vladeta Jovovic, Binary matrices up to row and column permutations
Index entries for sequences related to Boolean functions
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FORMULA
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a(n) = n*(n-1)/2 + Sum((n-2*i+1)*(n-2*i)/2, i=1..floor( (n+1)/2 )). - njas, Nov 28 2003
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CROSSREFS
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John Layman (layman(AT)calvin.math.vt.edu) observes that A003453 appears to be the alternating sum transform (PSumSIGN) of A005744.
Cf. A002623, A005745, A005746, A005747, A005748, A005771, A003180.
Cf. A052265.
Adjacent sequences: A005741 A005742 A005743 this_sequence A005745 A005746 A005747
Sequence in context: A008023 A008055 A137441 this_sequence A027367 A009879 A009878
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KEYWORD
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easy,nonn,nice
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AUTHOR
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njas, Simon Plouffe (plouffe(AT)math.uqam.ca)
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EXTENSIONS
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Additional comments from Alford Arnold (Alford1940(AT)aol.com)
More terms from Vladeta Jovovic (vladeta(AT)Eunet.yu), May 25 2000
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