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Search: id:A073717
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| A073717 |
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a(n)=T(2n), where T(n) are the tribonacci numbers A000073. |
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+0
1
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| 0, 1, 4, 13, 44, 149, 504, 1705, 5768, 19513, 66012, 223317, 755476, 2555757, 8646064, 29249425, 98950096, 334745777, 1132436852, 3831006429, 12960201916, 43844049029, 148323355432, 501774317241, 1697490356184, 5742568741225
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OFFSET
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0,3
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FORMULA
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a(n)=3a(n-1)+a(n-2)+a(n-3), a(0)=0, a(1)=1, a(2)=4. G.f.: (x+x^2)/(1-3x-x^2-x^3)
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MATHEMATICA
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CoefficientList[Series[(x+x^2)/(1-3x-x^2-x^3), {x, 0, 30}], x]
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CROSSREFS
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Cf. A000073.
Sequence in context: A027123 A027125 A027127 this_sequence A149427 A149428 A149429
Adjacent sequences: A073714 A073715 A073716 this_sequence A073718 A073719 A073720
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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 05 2002
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