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Search: id:A055274
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| 1, 7, 56, 448, 3584, 28672, 229376, 1835008, 14680064, 117440512, 939524096, 7516192768, 60129542144, 481036337152, 3848290697216, 30786325577728, 246290604621824, 1970324836974592, 15762598695796736, 126100789566373888
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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}->{1,2,3,4,5,6,7,8} such that for a fixed x in {1,2,...,n} and a fixed y in {1,2,3,4,5,6,7,8} 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, 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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G.f.: (1-x)/(1-8x). a(n)=7*8^(n-1); a(0)=1. a(n)=8a(n-1)+[(-1)^n]*C(1, 1-n).
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CROSSREFS
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Cf. A001018.
Sequence in context: A092315 A092318 A057090 this_sequence A126694 A024091 A082305
Adjacent sequences: A055271 A055272 A055273 this_sequence A055275 A055276 A055277
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, May 28 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), May 29 2000
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