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A111359
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Positive integers n such that the difference between the n-th prime and the sum of the divisors of n is congruent to 1 (mod n).
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0
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3, 6, 9, 10, 13, 42, 73, 184, 511, 690, 3275, 18918, 20574, 21340, 44140, 116669, 543214, 567016, 637321, 688792, 878649, 2582446, 27067133, 152149612, 180031091, 180397517, 290516940, 303713151, 749973242, 1138167152, 1149871982, 1340024880, 1992196101
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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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EXAMPLE
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The 42nd prime is 181. The divisors of 42 are 1, 2, 3, 6, 7, 14, 21, 42 and their sum is 96. 181-96 = 85. 85 = 1 mod 42. So 42 is a term.
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MATHEMATICA
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Select[Range[10^8], Mod[Prime[ # ] - Plus @@ Divisors[ # ], # ] == 1 &] (* Ray Chandler, Nov 09 2005 *)
fQ[n_] := Mod[Prime[n] - DivisorSigma[1, n], n] == 1; t = {}; Do[ If[ fQ[n], AppendTo[t, n]], {n, 50000000}]; t (* Robert G. Wilson v *)
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PROG
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(PARI) n=0; forprime(p=1, 1e9, n++; if((p - sigma(n)) % n == 1, print1(n, ", "))) \\ Amiram Eldar, Jan 19 2019
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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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