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A074240
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Numbers k such that k-th prime = sigma(sigma(k)) + 1.
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0
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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sigma(sigma(110)) + 1 = sigma(216) + 1 = 601 = prime(110).
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MATHEMATICA
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Select[Range[10^6], Prime[ # ] == DivisorSigma[1, DivisorSigma[1, # ]] + 1 &]
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PROG
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(MuPAD) ind := 1; nu := 2; repeat w := numlib::sigma(numlib::sigma(ind))+1; if w = nu then print(ind); end_if; ind := ind+1; nu := nextprime(nu+1); until ind>3400000 end_repeat; (Steinerberger)
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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