27463domain: NAppears in sequencesNumber of n X 2 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing.at n=27A229439Numbers k such that k!6 - 18 is prime, where k!6 is the sextuple factorial number (A085158).at n=31A289696