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A120298
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Largest prime factor of the n-th central factorial number A001819(n).
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1
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5, 7, 41, 479, 59, 266681, 63397, 514639, 178939, 242101, 18500393, 40799043101, 190297, 1844659, 78206663, 616798327, 38512247, 86364397717734821, 421950627598601, 84786899, 52030193, 31411862913089, 1422157053067, 47961582392203, 8408339, 6269019298981
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OFFSET
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2,1
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LINKS
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FORMULA
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MATHEMATICA
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Table[Max[FactorInteger[Sum[1/i^2, {i, 1, n}]/Product[1/i^2, {i, 1, n}]]], {n, 2, 30}]
Table[FactorInteger[n!^2*HarmonicNumber[n, 2]][[-1, 1]], {n, 2, 30}] (* Harvey P. Dale, Jul 29 2023 *)
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PROG
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(PARI) a(n) = vecmax(factor(n!^2 * sum(k=1, n, 1/k^2))[, 1]); \\ Daniel Suteu, Jun 10 2022
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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