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A085378
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Difference between primes p and the largest prime divisor of p-1.
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1
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3, 4, 6, 10, 15, 16, 12, 22, 26, 34, 36, 36, 24, 40, 30, 56, 56, 64, 70, 66, 42, 78, 94, 96, 86, 54, 106, 106, 120, 118, 120, 116, 112, 146, 144, 160, 84, 130, 90, 176, 172, 190, 190, 188, 204, 186, 114, 210, 204, 222, 236, 246, 255, 132, 202, 266, 254, 274, 236
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OFFSET
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3,1
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COMMENTS
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This sequence contains only one prime number, the 3.
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LINKS
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EXAMPLE
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For prime 107 we have 107 - 53 = 54.
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MAPLE
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end proc:
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MATHEMATICA
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#-FactorInteger[#-1][[-1, 1]]&/@Prime[Range[3, 70]] (* Harvey P. Dale, Jan 04 2012 *)
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PROG
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(PARI) cminuspm1(n) = \ prime - maxprime of prime-1 { forprime(x=5, n, forstep(p=x, 2, -1, if(isprime(p) & (x-1)%p==0, print1(x-p, ", "); break); ) ) }
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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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STATUS
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approved
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