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Search: id:A026569
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| A026569 |
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a(n)=T(n,n), T given by A026568. Also a(n) = number of integer strings s(0),...,s(n) counted by T, such that s(n)=0. |
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7
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| 1, 1, 3, 5, 13, 27, 67, 153, 375, 893, 2189, 5319, 13089, 32155, 79479, 196573, 487833, 1212135, 3018355, 7525585, 18792303, 46980373, 117589689, 294613155, 738844719, 1854484305, 4658460165, 11710592711, 29458662005, 74151824271
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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J. W. Layman, The Hankel Transform and Some of its Properties, J. Integer Sequences, 4 (2001), #01.1.5.
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FORMULA
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a(n)=sum{k=0..floor(n/2), binomial(2k, k)binomial(n-k, k)} - Paul Barry (pbarry(AT)wit.ie), Sep 09 2004
G.f.: sqrt[1/((1-x)(1-x-4x^2))]. - Ralf Stephan, Jan 08 2004
n*a(n)=(2*n-1)*a(n-1)+(3*n-3)*a(n-2)-(4*n-6)*a(n-3). - Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 12 2005
a(n)=sum{k=0..n, C(k, n-k)C(2(n-k), n-k)}; - Paul Barry (pbarry(AT)wit.ie), Jul 30 2005
G.f.: 1/(1-x-2x^2/(1-0x-x^2/(1-x-x^2/(1-0x-2x^2/(1-x-x^2/.... (continued fraction). [From Paul Barry (pbarry(AT)wit.ie), Dec 07 2008]
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CROSSREFS
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Sequence in context: A141630 A084173 A000631 this_sequence A035082 A005198 A160823
Adjacent sequences: A026566 A026567 A026568 this_sequence A026570 A026571 A026572
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu)
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