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A085271 Difference between n-th composite number and its smallest prime divisor. 4
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; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
For composite number 91 we have 91-7 = 84.
MATHEMATICA
#-FactorInteger[#][[1, 1]]&/@Complement[Range[2, 200], Prime[Range[PrimePi[200]]]] (* Harvey P. Dale, Dec 11 2010 *)
#-Divisors[#][[2]]&/@Select[Range[4, 200], !PrimeQ[#]&] (* Zak Seidov, Apr 09 2011 *)
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
CROSSREFS
Sequence in context: A050827 A082990 A099188 * A347376 A260812 A003972
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Aug 12 2003
EXTENSIONS
Typo in data corrected by Zak Seidov, Apr 09 2011
STATUS
approved

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Last modified April 19 02:45 EDT 2024. Contains 371782 sequences. (Running on oeis4.)