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A245527
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Number of compositions of n into parts 4 and 5 with at least one 4 and one 5.
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2
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0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 3, 3, 0, 0, 4, 6, 4, 0, 5, 10, 10, 5, 6, 15, 20, 15, 13, 21, 35, 35, 29, 35, 56, 70, 65, 64, 92, 126, 136, 129, 156, 219, 263, 265, 285, 375, 484, 528, 550, 660, 860, 1013, 1078, 1210, 1521, 1873, 2092, 2288, 2732, 3394
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OFFSET
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0,10
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (-1, -1, -1, 1, 3, 3, 3, 2, -1, -2, -2, -2, -1).
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FORMULA
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a(n) = a(n-4)+a(n-5)+b(n) where b(n) is the 20-cycle (1,0,0,1,0,1,0,1,0,0,1,1,0,0,0,2,0,0,0,1) and b(n)=b(n-20). Initial values are b(14)=1, a(9)=2, a(10)=0, a(11)=0, a(12)=0, a(13)=3.
G.f.: 1+1/(1-x^5-x^4)-1/(1-x^5)-1/(1-x^4) (see comment A245332). - courtesy of Joerg Arndt
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EXAMPLE
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a(22)=10 The tuples are (55444)(54544)(54454)... where a(22)=5!/3!2!=10.
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MATHEMATICA
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CoefficientList[Series[1 + 1/(1 - x^5 - x^4) - 1/(1 - x^5) - 1/(1 - x^4), {x, 0, 60}], x] (* Wesley Ivan Hurt, Jul 26 2014 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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