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 A290770 a(n) = Product_{k=1..n} k^(2*k). 1
 1, 1, 16, 11664, 764411904, 7464960000000000, 16249593066946560000000000, 11020848942410302096869949440000000000, 3102093199396597590886754340698424229232640000000000, 465607547420733489126893933985879279492195953053596584509440000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS G. C. Greubel, Table of n, a(n) for n = 0..27 Eric Weisstein's World of Mathematics, Hyperfactorial FORMULA a(n) = A002109(n)^2. a(n) = A185141(n)/A000178(n-1)^2 for n > 0. a(n) = (n!)^(2*n)/G(n+1)^2, where G() is the Barnes G-function. a(n) ~ A^2*exp(-n^2/2)*n^(n*(n+1))*n^(1/6), where A is the Glaisher-Kinkelin constant (A074962). MATHEMATICA Table[Product[k^(2 k), {k, 1, n}], {n, 0, 9}] Table[Hyperfactorial[n]^2, {n, 0, 9}] Table[n!^(2 n)/BarnesG[n + 1]^2, {n, 0, 9}] PROG (PARI) a(n) = prod(k=1, n, k^(2*k)) \\ Felix FrÃ¶hlich, Aug 10 2017 (MAGMA) [1] cat [(&*[k^(2*k): k in [1..n]]): n in [1..10]]; // G. C. Greubel, Oct 14 2018 CROSSREFS Cf. A000178, A001044, A001818, A002109, A051675, A055209, A061742, A062206, A074962, A184877, A185141, A260122. Sequence in context: A017092 A265634 A191945 * A223102 A167062 A233140 Adjacent sequences:  A290767 A290768 A290769 * A290771 A290772 A290773 KEYWORD nonn,easy AUTHOR Ilya Gutkovskiy, Aug 10 2017 STATUS approved

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Last modified June 29 15:47 EDT 2022. Contains 354913 sequences. (Running on oeis4.)