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A037980
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a(n) = (1/16)*( binomial(4*n, 2*n) - (-1)^n*binomial(2*n, n) + (1-(-1)^n)*binomial(2*n, n)^2 ).
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2
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0, 1, 4, 109, 800, 19501, 168952, 3979830, 37566720, 862687045, 8615396504, 193710517650, 2015475061184, 44516469004294, 478043160040240, 10399216983867484, 114539008771344384, 2459029841101222485, 27657033766735102744, 586949749681986718650, 6719200545824895620800, 141147097812860184921810
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OFFSET
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0,3
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REFERENCES
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The right-hand side of a binomial coefficient identity in H. W. Gould, Combinatorial Identities, Morgantown, 1972. (see Identity (3.75) divided by four in H. W. Gould, Combinatorial Identities, Morgantown, 1972, page 31.)
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LINKS
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FORMULA
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a(n) = (1/16)*(binomial(4*n, 2*n) - (-1)^n*binomial(2*n, n) + (1-(-1)^n)*binomial(2*n, n)^2).
a(n) = (1/4)*Sum_{k=0..floor((n-1)/2)} binomial(2*n, 2*k+1)^2.
G.f.: (1/16)*(sqrt(1 + sqrt(1-16*x))/(sqrt(2)*sqrt(1-16*x)) - 1/sqrt(1+4*x)) + (1/(8*Pi))*( EllipticK(16*x) - EllipticK(-16*x)). (End)
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MAPLE
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binomial(4*n, 2*n) -(-1)^n*binomial(2*n, n)+(1-(-1)^n)*binomial(2*n, n)^2 ;
%/16 ;
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MATHEMATICA
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With[{B=Binomial}, Table[(1/16)*(B[4*n, 2*n] +B[2*n, n]^2 -2*(-1)^n*B[B[2*n, n] +1, 2]), {n, 0, 30}]] (* G. C. Greubel, Jun 22 2022 *)
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PROG
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(Magma) [(1/16)*((2*n+1)*Catalan(2*n) -(-1)^n*(n+1)*Catalan(n) +(1-(-1)^n)*(n+1)^2*Catalan(n)^2): n in [0..30]]; // G. C. Greubel, Jun 22 2022
(SageMath) b=binomial; [(1/16)*(b(4*n, 2*n) -(-1)^n*b(2*n, n) +(1-(-1)^n)*b(2*n, n)^2) for n in (0..30)] # G. C. Greubel, Jun 22 2022
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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