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Search: id:A055988
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| A055988 |
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Sequence is its own 4th difference. |
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+0
5
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| 1, 2, 7, 26, 95, 345, 1252, 4544, 16493, 59864, 217286, 788674, 2862617, 10390321, 37713313, 136886433, 496850954, 1803399103, 6545722210, 23758733815, 86236081273, 313007493212, 1136110191472, 4123691589365, 14967590689568
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OFFSET
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1,2
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COMMENT
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Row sums of Riordan array (1/(1-x), x/(1-x)^4), A109960. - Paul Barry (pbarry(AT)wit.ie), Jul 06 2005
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FORMULA
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a(n)=5a(n-1)-6a(n-2)+4a(n-3)-a(n-4) =a(n-1)+A055991(n-1) =A055989(n)-A055989(n-1) =A055990(n)-2*A055990(n-1)+A055990(n-2)
G.f.: (1-x)^3/(1-5x+6x^2-4x^3+x^4); a(n)=sum{k=0..n, binomial(n+3k, 4k)}. - Paul Barry (pbarry(AT)wit.ie), Jul 06 2005
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CROSSREFS
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Cf. A055989, A055990, A055991 for the other differences of a(n). See A000079, A001906, A052529 for examples of sequences which are respectively their own first, second and third differences.
Sequence in context: A134063 A087448 A129273 this_sequence A001075 A113436 A126223
Adjacent sequences: A055985 A055986 A055987 this_sequence A055989 A055990 A055991
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KEYWORD
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nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Jun 02 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 05 2000
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