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 A117541 #5 Feb 05 2014 20:18:18 %S A117541 1,2,6,9,56,23,399,442,2220,2386,71577,22001,1179483,1156519,4975079 %N A117541 Number of permutations P of 1..n such that in P and in the inverse of P, every pair of adjacent numbers are relatively prime. %C A117541 Sequence suggested by _Leroy Quet_ on the SeqFan mailing list. %e A117541 a(4)=9, since the 9 permutations (1,2,3,4), (1,4,3,2), (2,1,3,4), (2,1,4,3), (2,3,4,1), (4,1,2,3), (3,2,1,4), (3,4,1,2), (4,3,2,1) satisfy the property. %Y A117541 Cf. A076220, A117542. %K A117541 nonn %O A117541 1,2 %A A117541 _Giovanni Resta_, Mar 28 2006