%I #19 Mar 06 2021 02:11:17

%S 1,1,3,8,46,176,955,5446,36122,259084,2043944,17371318,159616680,

%T 1566391958

%N (Number of permutations of {1,2,...,n} for which sums of adjacent numbers are all distinct)/2n.

%C Essentially different ways 1,2,3,...,n can be placed around a circle so that sums of adjacent numbers are distinct.

%H Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a040/A040018.java">Java program</a> (github)

%Y Cf. A091217, A006967.

%K nonn,hard,more

%O 3,3

%A _Erich Friedman_

%E a(10) from _Vladeta Jovovic_, Aug 25 2007

%E a(11)-a(13) from _Steve Butler_, Feb 08 2012

%E a(14)-a(16) from _Sean A. Irvine_, Mar 05 2021