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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
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| 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
| CoefficientList[Series[(x+x^2)/(1-3x-x^2-x^3), {x, 0, 30}], x]
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CROSSREFS
| Cf. A000073.
Sequence in context: A027123 A027125 A027127 * A149427 A149428 A149429
Adjacent sequences: A073714 A073715 A073716 * A073718 A073719 A073720
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KEYWORD
| easy,nonn
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AUTHOR
| Mario Catalani (mario.catalani(AT)unito.it), Aug 05 2002
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