Colouring a Loop (noch nicht übersetzt)

Problem 671

A certain type of flexible tile comes in three different sizes - 1×1, 1×2, and 1×3 - and in k different colours. There is an unlimited number of tiles available in each combination of size and colour.

These are used to tile a closed loop of width 2 and length (circumference) n, where n is a positive integer, subject to the following conditions:

  • The loop must be fully covered by non-overlapping tiles.
  • It is not permitted for four tiles to have their corners meeting at a single point.
  • Adjacent tiles must be of different colours.

For example, the following is an acceptable tiling of a 2×23 loop with k=4 (blue, green, red and yellow):

Acceptable colouring

but the following is not an acceptable tiling, because it violates the "no four corners meeting at a point" rule:

Unacceptable colouring

Let Fk(n) be the number of ways the 2×n loop can be tiled subject to these rules when k colours are available. (Not all k colours have to be used.) Where reflecting horizontally or vertically would give a different tiling, these tilings are to be counted separately.

For example, F4(3)=104, F5(7)=3327300, and F6(101)75309980(mod1000004321).

Find F10(10004003002001)mod1000004321.