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A342660
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The largest prime that divides the n-th multiply perfect number: a(n) = A006530(A007691(n)); a(1) = 1.
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4
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1, 3, 7, 5, 31, 7, 127, 7, 13, 31, 19, 31, 8191, 31, 31, 73, 73, 127, 131071, 19, 19, 89, 151, 127, 524287, 151, 127, 31, 127, 89, 89, 127, 61, 17, 3851, 1093, 151, 257, 911, 331, 2147483647, 3851, 911, 127, 257, 1093, 331, 331, 337, 337, 337, 257, 683, 3851, 8191, 1093, 257, 911, 3851, 1093, 178481, 8191, 337, 8191
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OFFSET
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1,2
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LINKS
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FORMULA
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MATHEMATICA
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Map[FactorInteger[#][[-1, 1]] &, Select[Range[10^6], IntegerQ@ DivisorSigma[-1, #] &] ] (* or, using the b-file at A007691: *)
Map[FactorInteger[#][[-1, 1]] &, DeleteCases[Import["https://oeis.org/A007691/b007691.txt", "Data"], _?(Length@ # == 0 &)][[1 ;; 64, -1]] ] (* Michael De Vlieger, Mar 19 2021 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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