107407domain: NAppears in sequencesThe length of the longest initial sequence of the form UHUH..., summed over all bargraphs having semiperimeter n (n>=2).at n=11A274495G.f.: Sum_{n=-oo..+oo} x^(n*(n+1)/2) * C(x)^(3*n-3), where C(x) = 1 + x*C(x)^2 is the g.f. of the Catalan numbers (A000108).at n=36A355348