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Search: id:A074678
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| A074678 |
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a(n)=Sum((-1)^(i+Floor(n/2))S(2i+e),(i=0,..,Floor(n/2))), where S(n) are generalized tribonacci numbers (A001644) and e=(1/2)(1-(-1)^n). |
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3
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| 3, 1, 0, 6, 11, 15, 28, 56, 103, 185, 340, 630, 1159, 2127, 3912, 7200, 13243, 24353, 44792, 82390, 151539, 278719, 512644, 942904, 1734271, 3189817, 5866988, 10791078, 19847887, 36505951, 67144912, 123498752, 227149619, 417793281
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) is the convolution of S(n) with the sequence (1,0,-1,0,1,0,-1,0,....) A056594.
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FORMULA
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a(n)=a(n-1)+2a(n-3)+a(n-4)+a(n-5), a(0)=3, a(1)=1, a(2)=0, a(3)=6, a(4)=11. G.f.: (3 - 2*x - x^2)/(1 - x - 2*x^3 - x^4 - x^5).
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MATHEMATICA
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CoefficientList[ Series[(3 - 2*x - x^2)/(1 - x - 2*x^3 - x^4 - x^5), {x, 0, 40}], x]
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CROSSREFS
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Cf. A001644, A056594.
Sequence in context: A137651 A058152 A058140 this_sequence A130888 A010601 A110504
Adjacent sequences: A074675 A074676 A074677 this_sequence A074679 A074680 A074681
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KEYWORD
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easy,nonn
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AUTHOR
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Mario Catalani (mario.catalani(AT)unito.it), Aug 30 2002
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