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 A274306 a(n) = Product_{k=1..n} (4*k^4+1). 2
 1, 5, 325, 105625, 108265625, 270772328125, 1403954521328125, 13484983177356640625, 220951449360988556640625, 5798870788479144669033203125, 231960630409954265905997158203125, 13584774319958971582784723570166015625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Erhan Gürel, On the Occurrence of Perfect Squares Among Values of Certain Polynomial Products, The American Mathematical Monthly 123.6 (2016): 597-599. FORMULA a(n) ~ (1 + cosh(Pi)) * 2^(2*n + 2) * n^(4*n + 2) / exp(4*n). - Vaclav Kotesovec, Oct 10 2016 MATHEMATICA Table[Product[4*k^4+1, {k, 1, n}], {n, 0, 15}] (* Vaclav Kotesovec, Oct 10 2016 *) PROG (PARI) a(n) = prod(k=1, n, 4*k^4+1); \\ Michel Marcus, Oct 10 2016 CROSSREFS For squares in this sequence see A274307. Cf. A255434. Sequence in context: A304212 A212041 A251696 * A053516 A085523 A292687 Adjacent sequences:  A274303 A274304 A274305 * A274307 A274308 A274309 KEYWORD nonn AUTHOR N. J. A. Sloane, Jun 20 2016 STATUS approved

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Last modified April 19 22:22 EDT 2019. Contains 322291 sequences. (Running on oeis4.)