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A067531
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Numbers n such that n - number of divisors of n is a prime.
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4
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5, 6, 7, 13, 15, 16, 19, 21, 27, 31, 33, 35, 43, 51, 57, 61, 65, 73, 77, 87, 93, 103, 105, 109, 111, 135, 139, 141, 143, 151, 155, 161, 165, 177, 181, 183, 185, 189, 193, 199, 201, 203, 215, 229, 231, 237, 241, 245, 267, 271, 275, 283, 285, 287, 313, 321, 335
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OFFSET
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1,1
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COMMENTS
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Larger of the twin primes (A006512) is a term.
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LINKS
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EXAMPLE
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51 is a term as d(51) = 4 and 51-4 = 47 is a prime.
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MAPLE
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with(numtheory): for n from 3 to 500 do if isprime(n-tau(n)) then printf(`%d, `, n) fi:od: # James A. Sellers, Feb 18 2002
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MATHEMATICA
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Select[Range[400], PrimeQ[#-DivisorSigma[0, #]]&] (* Harvey P. Dale, May 22 2013 *)
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CROSSREFS
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KEYWORD
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easy,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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