144476domain: NAppears in sequencesNumber of Twopins positions.at n=29A005690Number of Greek-key tours on a 6 X n grid.at n=6A160240Number of Greek-key tours on a 7 X n grid.at n=5A160241G.f. satisfies: A(x) = 1 + Sum_{n>=1} x^(n+1) * A(x)^n/(1 - x*A(x)^(2*n)).at n=13A192405