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A046665
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Largest prime divisor of n - smallest prime divisor of n (a(1)=0).
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18
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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;
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,10
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COMMENTS
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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
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REFERENCES
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Handbook of Number Theory, D. S. Mitrinovic et al., Kluwer, Section IV.1.
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LINKS
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FORMULA
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MAPLE
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a:= n-> `if`(n=1, 0, (s-> max(s)-min(s))(numtheory[factorset](n))):
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MATHEMATICA
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lpd[n_]:=Module[{fi=FactorInteger[n]}, fi[[-1, 1]]-fi[[1, 1]]]; Array[lpd, 90] (* Harvey P. Dale, Dec 31 2017 *)
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PROG
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(Haskell)
(PARI) a(n)={if(n==1, 0, my(f=factor(n)[, 1]); f[#f]-f[1])} \\ Andrew Howroyd, Mar 07 2020
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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