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 A326856 E.g.f.: Product_{k>=1} (1 + x^(4*k-3) / (4*k-3)). 3
 1, 1, 0, 0, 0, 24, 144, 0, 0, 40320, 403200, 0, 0, 479001600, 8643317760, 29059430400, 0, 20922789888000, 475108274995200, 1871463083212800, 0, 2432902008176640000, 76354225980899328000, 525098781423304704000, 0, 620448401733239439360000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS In general, if c > 0, mod(d,c) <> 0 and e.g.f. = Product_{k>=1} (1 + x^(c*k+d) / (c*k+d)), then a(n) ~ n! * Gamma(1 + d/c) / (c^(1/c) * exp(gamma/c) * Gamma(1/c) * Gamma(1 + (d+1)/c) * n^(1 - 1/c)), where gamma is the Euler-Mascheroni constant A001620 and Gamma() is the Gamma function. LINKS Vaclav Kotesovec, Table of n, a(n) for n = 0..440 Vaclav Kotesovec, Graph - the asymptotic ratio (40000 terms) FORMULA a(n) ~ n! / (sqrt(2*Pi) * exp(gamma/4) * n^(3/4)), where gamma is the Euler-Mascheroni constant A001620. MATHEMATICA nmax = 30; CoefficientList[Series[Product[(1+x^(4*k-3)/(4*k-3)), {k, 1, Floor[nmax/4]+1}], {x, 0, nmax}], x] * Range[0, nmax]! CROSSREFS Cf. A007838, A088994, A326780, A326855. Sequence in context: A223471 A219988 A316928 * A076835 A007900 A158874 Adjacent sequences:  A326853 A326854 A326855 * A326857 A326858 A326859 KEYWORD nonn AUTHOR Vaclav Kotesovec, Jul 27 2019 STATUS approved

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Last modified January 21 03:58 EST 2022. Contains 350473 sequences. (Running on oeis4.)