67108872domain: NAppears in sequencesNumber of ways of 4-coloring a map in which there is a central circle surrounded by an annulus divided into n-1 regions. There are n regions in all.at n=21A090860A Jacobsthal-Lucas convolution.at n=24A099429a(n) = 8*(2^n + 1).at n=23A175161a(n) = 2^n + 8.at n=26A242475