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Search: id:A075676
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| A075676 |
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a(n)=(1/2)(-(-1)^n+1)T(n)+(1/2)((-1)^n+1)S(n), where T(n)=tribonacci numbers A000073, S(n)=generalized tribonacci numbers A001644. |
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+0
1
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| 3, 1, 3, 2, 11, 7, 39, 24, 131, 81, 443, 274, 1499, 927, 5071, 3136, 17155, 10609, 58035, 35890, 196331, 121415, 664183, 410744, 2246915, 1389537, 7601259, 4700770, 25714875, 15902591, 86992799, 53798080, 294294531, 181997601
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OFFSET
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0,1
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COMMENT
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a(n)=T(n) if n odd, a(n)=S(n) if n even. a(n)=T(n)+((-1)^n+1)T(n-1)+(3/2)((-1)^n+1)T(n-2).
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FORMULA
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a(n)=3a(n-2)+a(n-4)+a(n-6), a(0)=3, a(1)=1, a(2)=3, a(3)=2, a(4)=11, a(5)=7. Ogf (3+x-6x^2-x^3-x^4)/(1-3x^2-x^4-x^6).
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MATHEMATICA
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CoefficientList[Series[(3+x-6x^2-x^3-x^4)/(1-3x^2-x^4-x^6), {x, 0, 40}], x]
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CROSSREFS
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Cf. A000073, A001644, A005013, A005247, A075536.
Sequence in context: A133916 A058589 A112164 this_sequence A124814 A122567 A122431
Adjacent sequences: A075673 A075674 A075675 this_sequence A075677 A075678 A075679
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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), Sep 24 2002
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