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Search: id:A055996
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| A055996 |
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a(n)=81*10^(n-2), a(0)=1, a(1)=8. |
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+0
2
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| 1, 8, 81, 810, 8100, 81000, 810000, 8100000, 81000000, 810000000, 8100000000, 81000000000, 810000000000, 8100000000000, 81000000000000, 810000000000000, 8100000000000000, 81000000000000000, 810000000000000000
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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For n>=2, a(n) is equal to the number of functions f:{1,2,...,n}->{1,2,3,4,5,6,7,8,9,10} such that for fixed, different x_1, x_2 in {1,2,...,n} and fixed y_1, y_2 in {1,2,3,4,5,6,7,8,9,10} we have f(x_1)<>y_1 and f(x_2)<> y_2. - Milan R. Janjic (agnus(AT)blic.net), Apr 19 2007
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REFERENCES
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pps. 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)=10a(n-1)+[(-1)^n]*C(2, 2-n). G.f.(x)=(1-x)^2/(1-10x).
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CROSSREFS
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Second differences of 10^n (A011557). Cf. A052268.
Sequence in context: A027768 A007792 A098308 this_sequence A068617 A007778 A065440
Adjacent sequences: A055993 A055994 A055995 this_sequence A055997 A055998 A055999
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, Jun 04 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 08 2000
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