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A066076
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Primes p such that there is a unique solution to p = sigma(x) - 1.
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13
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2, 3, 5, 7, 13, 19, 29, 37, 43, 61, 67, 73, 101, 109, 137, 149, 157, 163, 173, 193, 197, 199, 211, 229, 241, 257, 277, 281, 283, 313, 317, 331, 337, 347, 349, 353, 367, 373, 379, 397, 401, 409, 421, 457, 461, 463, 487, 499, 509, 523, 541
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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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If A066075(m)=1, then p(m) is here.
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MATHEMATICA
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With[{s = KeySort@ PositionIndex@ Array[DivisorSigma[1, #] - 1 &, 10^5]}, Take[#, 51] &@ Keys@ KeySelect[s, PrimeQ@ # && Length@ Lookup[s, #] == 1 &]] (* Michael De Vlieger, Jul 16 2017 *)
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PROG
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(PARI) { n=0; for (m=1, 10^9, p=prime(m); a=1; for (x=1, p - 1, if (p == (sigma(x) - 1), a++; break)); if (a==1, write("b066076.txt", n++, " ", p); if (n==1000, return)) ) } \\ Harry J. Smith, Nov 10 2009
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CROSSREFS
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Cf. A000040, A000203, A058340, A066071, A066072, A066073, A066074, A066075, A066076, A066077, A066080.
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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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