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A079084
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Greatest prime factor of (prime(n)+1)*(prime(n+1)+1)/4.
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3
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3, 3, 3, 3, 7, 7, 5, 5, 5, 5, 19, 19, 11, 11, 3, 5, 31, 31, 17, 37, 37, 7, 7, 7, 17, 17, 13, 11, 19, 19, 11, 23, 23, 7, 19, 79, 79, 41, 29, 29, 13, 13, 97, 97, 11, 53, 53, 19, 23, 23, 13, 11, 11, 43, 43, 11, 17, 139, 139, 71, 71, 11, 13, 157, 157, 83, 83, 29, 29, 59, 59, 23, 23, 19
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OFFSET
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1,1
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LINKS
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FORMULA
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MATHEMATICA
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a[n_]:=FactorInteger[(Prime[n]+1)(Prime[n+1]+1)/4][[-1, 1]]; Table[a[n], {n, 1, 74}] (* Jean-François Alcover, Mar 18 2011 *)
FactorInteger[(First[#]+1) (Last[#]+1)/4][[-1, 1]]&/@Partition[Prime[ Range[100]], 2, 1] (* Harvey P. Dale, Nov 14 2011 *)
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PROG
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(Haskell)
(PARI) a(n) = my(f=factor((prime(n)+1)*(prime(n+1)+1)/4)); f[#f~, 1]; \\ Michel Marcus, Nov 12 2023
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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STATUS
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approved
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