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 A046665 Largest prime divisor of n - smallest prime divisor of n (a(1)=0). 15
 0, 0, 0, 0, 0, 1, 0, 0, 0, 3, 0, 1, 0, 5, 2, 0, 0, 1, 0, 3, 4, 9, 0, 1, 0, 11, 0, 5, 0, 3, 0, 0, 8, 15, 2, 1, 0, 17, 10, 3, 0, 5, 0, 9, 2, 21, 0, 1, 0, 3, 14, 11, 0, 1, 6, 5, 16, 27, 0, 3, 0, 29, 4, 0, 8, 9, 0, 15, 20, 5, 0, 1, 0, 35, 2, 17, 4, 11, 0, 3, 0, 39, 0, 5, 12, 41, 26, 9, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,10 COMMENTS Even nonzero terms correspond to odd composite numbers that are not powers of primes. Terms of A030173 appear in this sequence infinitely often. - Alonso del Arte, Nov 27 2011 A135093(n) = first occurrence of A030173(n). - Reinhard Zumkeller, Jul 03 2015 REFERENCES Handbook of Number Theory, D. S. Mitrinovic et al., Kluwer, Section IV.1. LINKS T. D. Noe, Table of n, a(n) for n=1..1000 FORMULA a(n) = A006530(n) - A020639(n). MATHEMATICA f[n_]:=Transpose[FactorInteger[n]][[1]]; Table[Last[f[n]-First[f[n]]], {n, 200}] (* Vladimir Joseph Stephan Orlovsky, Apr 08 2011 *) lpd[n_]:=Module[{fi=FactorInteger[n]}, fi[[-1, 1]]-fi[[1, 1]]]; Array[lpd, 90] (* Harvey P. Dale, Dec 31 2017 *) PROG (Haskell) a046665 n = a006530 n - a020639 n  -- Reinhard Zumkeller, Jul 03 2015 CROSSREFS Cf. A006530, A020639, A074320, A066048, A130064, A130065. Sequence in context: A100573 A049087 A178921 * A100574 A056100 A141665 Adjacent sequences:  A046662 A046663 A046664 * A046666 A046667 A046668 KEYWORD nonn,easy,nice AUTHOR EXTENSIONS More terms from James A. Sellers STATUS approved

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Last modified March 18 09:13 EDT 2018. Contains 300736 sequences. (Running on oeis4.)