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 A109810 Number of permutations of the positive divisors of n, where every element is coprime to its adjacent elements. 6
 1, 2, 2, 2, 2, 4, 2, 0, 2, 4, 2, 0, 2, 4, 4, 0, 2, 0, 2, 0, 4, 4, 2, 0, 2, 4, 0, 0, 2, 0, 2, 0, 4, 4, 4, 0, 2, 4, 4, 0, 2, 0, 2, 0, 0, 4, 2, 0, 2, 0, 4, 0, 2, 0, 4, 0, 4, 4, 2, 0, 2, 4, 0, 0, 4, 0, 2, 0, 4, 0, 2, 0, 2, 4, 0, 0, 4, 0, 2, 0, 0, 4, 2, 0, 4, 4, 4, 0, 2, 0, 4, 0, 4, 4, 4, 0, 2, 0, 0, 0, 2, 0, 2, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Depends only on prime signature; a(A033942(n))=0; a(A037143(n))>0; a(A000430(n))=2; a(A006881(n))=4. - Reinhard Zumkeller, May 24 2010 LINKS R. Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(1)=1, a(p) = 2, a(p^2) = 2, a(p*q) = 4 (where p and q are distinct primes), all other terms are 0. EXAMPLE The divisors of 6 are 1, 2, 3 and 6. Of the permutations of these integers, only (6,1,2,3), (6,1,3,2), (2,3,1,6) and (3,2,1,6) are such that every pair of adjacent elements is coprime. CROSSREFS Cf. A178254. - Reinhard Zumkeller, May 24 2010 Sequence in context: A306653 A132003 A122857 * A122066 A053238 A227783 Adjacent sequences:  A109807 A109808 A109809 * A109811 A109812 A109813 KEYWORD nonn AUTHOR Leroy Quet, Aug 16 2005 EXTENSIONS Terms 17 to 59 from Diana L. Mecum, Jul 18 2008 More terms from David Wasserman, Oct 01 2008 STATUS approved

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Last modified December 16 09:06 EST 2019. Contains 330020 sequences. (Running on oeis4.)