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A055846
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A second order recursive sequence.
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1
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1, 4, 25, 150, 900, 5400, 32400, 194400, 1166400, 6998400, 41990400, 251942400, 1511654400, 9069926400, 54419558400, 326517350400, 1959104102400, 11754624614400, 70527747686400, 423166486118400, 2538998916710400
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| For n>=2, a(n) is equal to the number of functions f:{1,2,...,n}->{1,2,3,4,5,6} 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} we have f(x_1)<>y_1 and f(x_2)<> y_2. - Milan R. Janjic (agnus(AT)blic.net), Apr 19 2007
a(n) is the number of generalized compositions of n when there are 5*i-1 different types of i, (i=1,2,...). [From Milan R. Janjic (agnus(AT)blic.net), Aug 26 2010]
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REFERENCES
| A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pps. 194-196.
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LINKS
| Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
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FORMULA
| a(n)=25*6^(n-2), a(0)=1, a(1)=4. a(n)=6a(n-1)+[(-1)^n]*binomial(2, 2-n); G.f.(x)=(1-x)^2/(1-6x).
a(n) = Sum_{k, 0<=k<=n} A201780(n,k)*4^k. - DELEHAM Philippe, Dec 05 2011
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CROSSREFS
| First differences of A052934. Cf. A000400.
Sequence in context: A079291 A173612 A072221 * A091634 A010909 A079750
Adjacent sequences: A055843 A055844 A055845 * A055847 A055848 A055849
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KEYWORD
| easy,nonn
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AUTHOR
| Barry E. Williams, Jun 03 2000
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 05 2000
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