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Search: id:A005562
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| A005562 |
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Number of walks on square lattice.
(Formerly M3974)
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+0
5
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| 1, 5, 35, 140, 720, 2700, 12375, 45375, 196625, 715715, 3006003, 10930920, 45048640, 164105760, 668144880, 2441298600, 9859090500, 36149998500
(list; graph; listen)
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OFFSET
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4,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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R. K. Guy, Catwalks, Sandsteps and Pascal Pyramids, J. Integer Seqs., Vol. 3 (2000), #00.1.6
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FORMULA
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a(n) = C(n+5, ceil(n/2))*C(n+4, floor(n/2)) - C(n+5, ceil((n-1)/2))*C(n+4, floor((n-1)/2)). - Paul D. Hanna (pauldhanna(AT)juno.com), Apr 16 2004
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PROGRAM
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(PARI) {a(n)=binomial(n+5, ceil(n/2))*binomial(n+4, floor(n/2)) - binomial(n+5, ceil((n-1)/2))*binomial(n+4, floor((n-1)/2))}
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CROSSREFS
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Cf. A005558-A005561, A093768.
Sequence in context: A096743 A026697 A000910 this_sequence A097872 A124793 A048515
Adjacent sequences: A005559 A005560 A005561 this_sequence A005563 A005564 A005565
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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