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A005557
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Number of walks on square lattice.
(Formerly M5277)
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7
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42, 132, 297, 572, 1001, 1638, 2548, 3808, 5508, 7752, 10659, 14364, 19019, 24794, 31878, 40480, 50830, 63180, 77805, 95004, 115101, 138446, 165416, 196416, 231880, 272272, 318087, 369852, 428127, 493506, 566618, 648128, 738738, 839188, 950257, 1072764
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OFFSET
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0,1
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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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FORMULA
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a(n) = A009766(n+5, 5) = (n+1)*binomial(n+10, 4)/5.
G.f.: (42 - 120*x + 135*x^2 - 70*x^3 + 14*x^4)/(1-x)^6; numerator polynomial is N(2;4, x) from A062991.
Sum_{n>=0} 1/a(n) = 2509/63504.
Sum_{n>=0} (-1)^n/a(n) = 951395/63504 - 1360*log(2)/63. (End)
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MAPLE
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[seq(binomial(n, 5)-binomial(n, 3), n=9..55)]; # Zerinvary Lajos, Jul 19 2006
A005557:=(42-120*z+135*z**2-70*z**3+14*z**4)#(z-1)**6; # conjectured by Simon Plouffe in his 1992 dissertation
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MATHEMATICA
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LinearRecurrence[{6, -15, 20, -15, 6, -1}, {42, 132, 297, 572, 1001, 1638}, 40] (* Harvey P. Dale, Feb 22 2024 *)
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PROG
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(GAP) List([0..30], n->(n+1)*Binomial(n+10, 4)/5); # Muniru A Asiru, Apr 10 2018
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CROSSREFS
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Sixth diagonal of Catalan triangle A033184.
Sixth column of Catalan triangle A009766.
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KEYWORD
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nonn,walk,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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