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 A152443 a(n) = the largest proper divisor of n that is coprime to d(n), where d(n) = the number of divisors of n. 1
 1, 1, 2, 1, 3, 1, 1, 1, 5, 1, 1, 1, 7, 5, 8, 1, 1, 1, 5, 7, 11, 1, 3, 5, 13, 9, 7, 1, 15, 1, 1, 11, 17, 7, 4, 1, 19, 13, 5, 1, 21, 1, 11, 5, 23, 1, 3, 7, 25, 17, 13, 1, 27, 11, 7, 19, 29, 1, 5, 1, 31, 7, 32, 13, 33, 1, 17, 23, 35, 1, 1, 1, 37, 25, 19, 11, 39, 1, 1, 27, 41, 1, 7, 17, 43, 29, 11, 1, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 LINKS Table of n, a(n) for n=2..90. EXAMPLE There are 4 divisors of 27. These are 1,3,9,27. The proper divisors of 27 are therefore 1,3,9. The largest of these that is coprime to d(27) = 4 is 9. So a(27) = 9. (Note that in this case, the largest divisor of 27 coprime to 4 is 27, not 9.) MATHEMATICA Table[Max[Select[Drop[Divisors[n], -1], GCD[DivisorSigma[0, n], # ] == 1 &]], {n, 2, 100}] (* Stefan Steinerberger, Dec 06 2008 *) CROSSREFS Cf. A137926, A152444. Sequence in context: A328917 A265917 A057021 * A119804 A300977 A144869 Adjacent sequences: A152440 A152441 A152442 * A152444 A152445 A152446 KEYWORD nonn AUTHOR Leroy Quet, Dec 04 2008 EXTENSIONS Extended by Ray Chandler and Stefan Steinerberger, Dec 05 2008 STATUS approved

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Last modified September 26 23:31 EDT 2023. Contains 365668 sequences. (Running on oeis4.)