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Search: id:A111177
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| A111177 |
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Number of base n numbers in which each digit appears only once (all unnecessary 0's deleted). |
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+0
1
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| 4, 21, 130, 913, 7176, 62629, 602806, 6356865, 72994348, 907497301, 12152572554, 174476220241, 2674434002800, 43603430324133, 753581024080126, 13763517571878529, 264919276238885076, 5360264479811601685
(list; graph; listen)
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OFFSET
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2,1
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FORMULA
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a(n)=Sum(i=0, n-1) (i^2+i+1)(n-1)!/(n-1-i)!; n>1
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EXAMPLE
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a(2)=4 because in the binary system only the numbers 0;1;0,1;10 can be written with each digit used only once (all unnecessary 0's deleted).
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MATHEMATICA
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f[n_] := Sum[(i^2 + i + 1)(n - 1)!/(n - 1 - i)!, {i, 0, n - 1}]; Table[ f[n], {n, 2, 19}] (* Robert G. Wilson v *)
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CROSSREFS
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Adjacent sequences: A111174 A111175 A111176 this_sequence A111178 A111179 A111180
Sequence in context: A032326 A007345 A099250 this_sequence A141052 A058308 A078591
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KEYWORD
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nonn
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AUTHOR
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Rafael Hofman (mathematics287(AT)yahoo.de), Oct 22 2005
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Oct 29 2005
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