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a(n) = Product_{k=0..n} (7*k)! / k!^7.
4

%I #5 Nov 23 2023 10:36:38

%S 1,5040,3432645216000,626489905645044080640000000,

%T 41646279370357699257014919153469440000000000000,

%U 1200992054275801322636044235924808416678612164215512865177600000000000000

%N a(n) = Product_{k=0..n} (7*k)! / k!^7.

%C In general, for m > 1, Product_{k=0..n} (m*k)! / k!^m ~ A^(m - 1/m) * exp(m*n/2 - m/12 + 1/(12*m) - n/2) * m^(m*n^2/2 + m*n/2 - 1/(12*m) + n/2) * n^(-m*n/2 - m/3 + 1/(12*m) + n/2 + 1/4) * (2*Pi)^(-m*n/2 - m/4 + n/2 + 1/4) / Product_{j=1..m-1} Gamma(j/m)^(j/m), where A is the Glaisher-Kinkelin constant A074962.

%F a(n) = Product_{k=0..n} binomial(7*k,k) * binomial(6*k,k) * binomial(5*k,k) * binomial(4*k,k) * binomial(3*k,k) * binomial(2*k,k).

%F a(n) = A271947(n) / A000178(n)^7.

%F a(n) ~ A^(48/7) * 7^(7*n^2/2 + 4*n - 1/84) * exp(3*n - 4/7) / (Gamma(1/7)^(1/7) * Gamma(2/7)^(2/7) * Gamma(3/7)^(3/7) * Gamma(4/7)^(4/7) * Gamma(5/7)^(5/7) * Gamma(6/7)^(6/7) * n^(3*n + 29/14) * (2*Pi)^(3*n + 3/2)), where A is the Glaisher-Kinkelin constant A074962.

%t Table[Product[(7*k)!/k!^7, {k, 0, n}], {n, 0, 10}]

%t Table[Product[Binomial[7*k,k] * Binomial[6*k,k] * Binomial[5*k,k] * Binomial[4*k,k] * Binomial[3*k,k] * Binomial[2*k,k], {k, 0, n}], {n, 0, 10}]

%Y Cf. A000178, A071549, A271947.

%Y Cf. A007685, A367567, A367568, A367569, A367570.

%K nonn

%O 0,2

%A _Vaclav Kotesovec_, Nov 23 2023