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 A307210 a(n) = Product_{i=1..n, j=1..n} (i^3 + j^3 + 1). 2
 3, 5100, 305727048000, 7748770873210669158912000, 476007332700693200670745550306381336371200000, 272661655519533773844144991586798737775635133552905539740860416000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Product_{i=1..n, j=1..n} (1 + 1/(i + j)) = A324444(n) / A079478(n) ~ 2^(2*n + 1) / (sqrt(Pi)*n^(3/2)). Product_{i=1..n, j=1..n} (1 + 1/(i^2 + j^2)) = A324443(n) / A324403(n) ~ c * n^(Pi/2), where c = A306398 * 2^(3/4) * exp(-Pi/12) * Pi^(1/4) * Gamma(3/4) = 0.36753062884677326134620846786416595535234038999313315993144237973600... LINKS FORMULA a(n) ~ A307209 * A324426(n). a(n) ~ c * A * 2^(2*n*(n+1) + 1/4) * exp(Pi*(n*(n+1) + 1/6)/sqrt(3) - 9*n^2/2 - 1/12) * n^(3*n^2 - 3/4) / (3^(5/6) * Pi^(1/6) * Gamma(2/3)^2), where c = A307209 = Product_{i>=1, j>=1} (1 + 1/(i^3 + j^3)) = 3.504782999339728375891120570... and A is the Glaisher-Kinkelin constant A074962. MATHEMATICA Table[Product[i^3 + j^3 + 1, {i, 1, n}, {j, 1, n}], {n, 1, 8}] CROSSREFS Cf. A307209, A324403, A324426, A324443, A324444. Sequence in context: A251603 A168556 A200950 * A171362 A249511 A248506 Adjacent sequences:  A307207 A307208 A307209 * A307211 A307212 A307213 KEYWORD nonn AUTHOR Vaclav Kotesovec, Mar 28 2019 STATUS approved

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Last modified September 27 08:39 EDT 2021. Contains 347689 sequences. (Running on oeis4.)