A282847 Given n people seated at a table, a(n) is the minimum number of swaps that must occur in order for everybody to have sat next to every other person.

0, 0, 0, 1, 3, 4, 4, 6, 8, 10, 12, 14, 17, 20

Offset

1,5

Comments

a(n) >= ceiling(n(n-3)/8).

Links

Table of n, a(n) for n=1..14.

Mathematics Stack Exchange, Making Friends around a Circular Table

Example

For n = 7 the a(7) = 4 swaps are:
(1) 1 swaps with 4,
(2) 1 swaps with 5,
(3) 3 swaps with 6, and then
(4) 2 swaps with 6.

Crossrefs

Sequence in context: A363527 A224212 A078490 * A363239 A047877 A351371

Adjacent sequences: A282844 A282845 A282846 * A282848 A282849 A282850

Keyword

nonn,hard,more

Author

Peter Kagey, Feb 24 2017

Extensions

a(13) and a(14) added by Dmitry Kamenetsky, Feb 26 2017

Status

approved