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A335618
E.g.f.: Sum_{n>=0} Product_{k=1..n} tan(2*k*x).
1
1, 2, 16, 304, 10496, 568832, 44486656, 4742354944, 660908343296, 116642430451712, 25425572550148096, 6708171660023824384, 2106760489114215120896, 776654121137653931835392, 332101031506139993274843136, 163037618505293422657351450624, 91075662529714266445615040823296
OFFSET
0,2
FORMULA
a(n) ~ 2^(n - 1/2) * n!^2 / G^(n+1), where G is the Catalan constant A006752.
a(n) = 2^n * A177382(n).
MATHEMATICA
nmax = 20; CoefficientList[Series[Sum[Product[Tan[2*k*x], {k, 1, n}], {n, 0, nmax}], {x, 0, nmax}], x] * Range[0, nmax]!
CROSSREFS
Sequence in context: A188985 A362734 A009250 * A174487 A140051 A264658
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Oct 02 2020
STATUS
approved