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Search: id:A059951
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| A059951 |
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10-block bicoverings of an n-set. |
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+0
30
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| 0, 0, 0, 0, 0, 0, 420, 154637, 20368816, 1775801814, 124151410020, 7596257673279, 426319554841752, 22564352299016528, 1146221298547133380, 56531610963314602401, 2728475248127447671008, 129586638359127411410442
(list; graph; listen)
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OFFSET
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1,7
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REFERENCES
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I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983.
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FORMULA
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a(n)=(1/10!)*(45^n-10*36^n-45*29^n+90*28^n+360*22^n-480*21^n+630*17^n-2520*16^n+2100*15^n-3780*12^n+10080*11^n-6552*10^n-3150*9^n+18900*8^n-31500*7^n+28560*6^n-46620*5^n+27720*4^n+85560*3^n-146160*2^n+83520). E.g.f. for m-block bicoverings of an n-set is exp(-x-1/2*x^2*(exp(y)-1))*Sum_{i=0..inf} x^i/i!*exp(binomial(i, 2)*y).
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CROSSREFS
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Cf. A002718, A059443, A003462, A059945-A059950.
Sequence in context: A135380 A035846 A046167 this_sequence A028683 A014890 A031784
Adjacent sequences: A059948 A059949 A059950 this_sequence A059952 A059953 A059954
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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.yu), Feb 14 2001
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