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A085271
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Difference between n-th composite number and its smallest prime divisor.
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2
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2, 4, 6, 6, 8, 10, 12, 12, 14, 16, 18, 18, 20, 22, 20, 24, 24, 26, 28, 30, 30, 32, 30, 34, 36, 36, 38, 40, 42, 42, 44, 46, 42, 48, 48, 50, 52, 50, 54, 54, 56, 58, 60, 60, 62, 60, 64, 66, 66, 68, 70, 72, 72, 74, 70, 76, 78, 78, 80, 82, 80, 84, 84, 86, 88, 84, 90, 90, 92, 90, 94
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| For composite number 91 we have 91-7 = 84
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MATHEMATICA
| #-FactorInteger[#][[1, 1]]&/@Complement[Range[2, 200], Prime[Range[PrimePi[200]]]]
#-Divisors[#][[2]]&/@Select[Range[4, 200], !PrimeQ[#]&](* Zak Seidov, Apr 09 2011 *)
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PROG
| (PARI) cminusp(n) = { for(x=2, n, forprime(p=2, floor(sqrt(x)), if(x%p==0, print1(x-p, ", "); break); ) ) }
(PARI){n=200; for(x=4, n, if(isprime(x), , print1(x-divisors(x)[2], ", ")))}[Zak Seidov, Apr 09 2011]
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CROSSREFS
| Cf. A085273.
Sequence in context: A050827 A082990 A099188 * A003972 A023853 A056526
Adjacent sequences: A085268 A085269 A085270 * A085272 A085273 A085274
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Aug 12 2003
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EXTENSIONS
| Mathematica program provided by Harvey P. Dale, Dec. 11, 2010
Typo in data corrected by Zak Seidov (zakseidov(AT)yahoo.com), Apr 09 2011
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