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A084127
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Prime factor >= other prime factor of n-th semiprime.
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43
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2, 3, 3, 5, 7, 5, 7, 11, 5, 13, 11, 17, 7, 19, 13, 23, 7, 17, 11, 19, 29, 31, 13, 23, 37, 11, 41, 17, 43, 29, 13, 31, 47, 19, 53, 37, 23, 59, 17, 11, 61, 41, 43, 19, 67, 47, 71, 13, 29, 73, 31, 79, 53, 23, 83, 13, 59, 89, 61, 37, 17, 97, 67, 101, 29, 41, 103, 19, 71, 107, 43, 31
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OFFSET
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1,1
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COMMENTS
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Largest nontrivial divisor of n-th semiprime. [Juri-Stepan Gerasimov, Apr 18 2010]
Greater of the prime factors of A001358(n). - Jianing Song, Aug 05 2022
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LINKS
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Zak Seidov, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Semiprime
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FORMULA
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a(n) = A006530(A001358(n)).
a(n) = A001358(n)/A020639(A001358(n)). [corrected by Michel Marcus, Jul 18 2020]
a(n) = A001358(n)/A084126(n).
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MATHEMATICA
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FactorInteger[#][[-1, 1]]& /@ Select[Range[1000], PrimeOmega[#] == 2&] (* Jean-François Alcover, Nov 17 2021 *)
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PROG
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(Haskell)
a084127 = a006530 . a001358 -- Reinhard Zumkeller, Nov 25 2012
(PARI) lista(nn) = {for (n=2, nn, if (bigomega(n)==2, f = factor(n); print1(f[length(f~), 1], ", ")); ); } \\ Michel Marcus, Jun 05 2013
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CROSSREFS
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Cf. A001358 (the semiprimes), A084126 (lesser of the prime factors of the semiprimes).
Cf. A014673, A061299, A068318, A087718, A087794, A089994, A089995, A096932, A106550, A106554, A108542, A126663, A131284, A138510, A138511.
Sequence in context: A066072 A239586 A180611 * A089934 A113460 A113470
Adjacent sequences: A084124 A084125 A084126 * A084128 A084129 A084130
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller, May 15 2003
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EXTENSIONS
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Corrected by T. D. Noe, Nov 15 2006
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STATUS
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approved
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