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Search: id:A052268
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| 1, 9, 90, 900, 9000, 90000, 900000, 9000000, 90000000, 900000000, 9000000000, 90000000000, 900000000000, 9000000000000, 90000000000000, 900000000000000, 9000000000000000
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OFFSET
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0,2
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COMMENT
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For n>=1, a(n) is equal to the number of functions f:{1,2...,n}->{1,2,...,10} such that for a fixed x in {1,2,...,n} and a fixed y in {1,2,...,10} we have f(x)<>y. - Aleksandar M. Janjic and Milan R. Janjic (agnus(AT)blic.net), Mar 27 2007
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REFERENCES
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
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LINKS
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Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
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FORMULA
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a(n)=9*10^(n-1); n >= 1; a(0)=1. a(n)=10a(n-1)+((-1)^n)C(1, 1-n); a(-1)=0.
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CROSSREFS
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Cf. A011557.
Sequence in context: A054616 A052386 A057092 this_sequence A036258 A098399 A082367
Adjacent sequences: A052265 A052266 A052267 this_sequence A052269 A052270 A052271
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, Feb 03 2000
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