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A339864
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Primes of the form p + sigma(p-1) for primes p.
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1
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3, 19, 29, 41, 59, 103, 131, 139, 151, 149, 229, 211, 269, 349, 269, 389, 439, 383, 523, 419, 449, 727, 701, 787, 569, 683, 719, 659, 991, 859, 811, 1009, 887, 1153, 877, 1109, 1489, 1489, 1223, 1327, 1657, 1579, 1259, 1693, 2221, 1409, 2011, 1607, 1831, 2251, 1867, 2503, 1801, 1811, 2677, 2689
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OFFSET
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1,1
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COMMENTS
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Terms are in order of increasing p.
Terms that occur more than once include 269, 1489, 2903, 3271, 5099, 7159.
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LINKS
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FORMULA
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EXAMPLE
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A339862(3) = 11 so a(3) = 11 + sigma(11-1) = 29.
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MAPLE
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select(isprime, map(t -> t + numtheory:-sigma(t-1), [seq(ithprime(i), i=1..200)]));
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MATHEMATICA
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Select[#+DivisorSigma[1, #-1]&/@Prime[Range[200]], PrimeQ] (* Harvey P. Dale, Jan 31 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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EXTENSIONS
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STATUS
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approved
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