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A085271 Difference between n-th composite number and its smallest prime divisor. 2
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

Table of n, a(n) for n=1..71.

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

Cf. A085273.

Sequence in context: A050827 A082990 A099188 * A260812 A003972 A023853

Adjacent sequences:  A085268 A085269 A085270 * A085272 A085273 A085274

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 August 15 22:40 EDT 2018. Contains 313782 sequences. (Running on oeis4.)