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A103665
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Primes p such that the number of divisors of p-1 is greater than the number of divisors of p+1.
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7
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13, 31, 37, 43, 61, 67, 73, 97, 101, 109, 113, 127, 151, 157, 163, 181, 193, 211, 229, 241, 257, 271, 277, 281, 283, 313, 331, 337, 353, 373, 379, 397, 401, 409, 421, 433, 457, 463, 487, 521, 523, 541, 547, 571, 577, 601, 613, 617, 631, 641, 661, 673, 677
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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a(1)=13 because d(12)=6 > d(14)=4.
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MATHEMATICA
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Select[Prime[Range[2, 140]], Length[Divisors[ # - 1]] > Length[Divisors[ # + 1]] &]
Select[Prime[Range[200]], DivisorSigma[0, #-1]>DivisorSigma[0, #+1]&] (* Harvey P. Dale, Aug 21 2022 *)
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PROG
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(PARI)
forprime (k=2, 700, if(numdiv(k-1)>numdiv(k+1), print1(k, ", ")))
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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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