This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A109810 #19 Oct 30 2022 05:27:57 %S A109810 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, %T A109810 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, %U A109810 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 %N A109810 Number of permutations of the positive divisors of n, where every element is coprime to its adjacent elements. %C A109810 Depends only on prime signature. - _Reinhard Zumkeller_, May 24 2010 %H A109810 Reinhard Zumkeller, <a href="/A109810/b109810.txt">Table of n, a(n) for n = 1..10000</a> %F A109810 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. %F A109810 a(A033942(n))=0; a(A037143(n))>0; a(A000430(n))=2; a(A006881(n))=4. - _Reinhard Zumkeller_, May 24 2010 %e A109810 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. %Y A109810 Cf. A178254. - _Reinhard Zumkeller_, May 24 2010 %K A109810 nonn %O A109810 1,2 %A A109810 _Leroy Quet_, Aug 16 2005 %E A109810 Terms 17 to 59 from _Diana L. Mecum_, Jul 18 2008 %E A109810 More terms from _David Wasserman_, Oct 01 2008