(MAGMAMagma) [Binomial(10*n, n): n in [0..50]]; // Vincenzo Librandi, Apr 21 2011
(MAGMAMagma) [Binomial(10*n, n): n in [0..50]]; // Vincenzo Librandi, Apr 21 2011
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From _Peter Bala, _, Feb 21 2022: (Start)
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From Peter Bala, Feb 21 2022: (Start)
The o.g.f. A(x) is algebraic: (1 - A(x))*(1 + 9*A(x))^9 + (10^10)*x*A(x)^10 = 0.
Sum_{n >= 1} a(n)*( x*(9*x + 10)^9/(10^10*(1 + x)^10) )^n = x. (End)
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From Peter Bala, Jan 17 2020: (Start)
a(n) = Sum_{k = 0..n} (k + 1)*binomial(10*n-k-2, n-k).
a(n) = Sum_{k = 0..n} (-1)^(n+k)*binomial(n*(x+9), k)*binomial(n*x-k-1, n-k), for arbitrary x. (End)
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