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A085393 Difference between the largest and the smallest prime factor of the greatest proper divisor of n. 3
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 1, 0, 0, 0, 5, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 3, 0, 4, 0, 9, 2, 0, 0, 1, 0, 0, 0, 11, 0, 0, 0, 5, 0, 0, 0, 3, 0, 0, 4, 0, 0, 8, 0, 15, 0, 2, 0, 1, 0, 0, 0, 17, 0, 10, 0, 3, 0, 0, 0, 5, 0, 0, 0, 9, 0, 2, 0, 21, 0, 0, 0, 1, 0, 0, 8, 3, 0, 14 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,20

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

FORMULA

a(n) = A085392(n) - A014673(n).

MATHEMATICA

PrimeFactors[n_] := Flatten[ Table[ # [[1]], {1}] & /@ FactorInteger[n]]; f[n_] := Block[{gpd = Divisors[n][[ -2]]}, If[gpd == 1, 0, PrimeFactors[gpd][[ -1]] - PrimeFactors[gpd][[1]] ]]; Table[ If[n == 1, 0, f[n]], {n, 1, 102}]

{1}~Join~Array[#[[-1, 1]] - #[[1, 1]] &@ FactorInteger@ Last@ Most@ Divisors@ # &, 101, 2] (* Michael De Vlieger, Dec 03 2017 *)

CROSSREFS

Cf. A014673, A085392.

Sequence in context: A046775 A221787 A204060 * A128980 A096693 A193139

Adjacent sequences:  A085390 A085391 A085392 * A085394 A085395 A085396

KEYWORD

nonn

AUTHOR

Robert G. Wilson v and Reinhard Zumkeller, Jun 26 2003

STATUS

approved

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Last modified October 1 11:01 EDT 2020. Contains 337442 sequences. (Running on oeis4.)