1937266domain: NAppears in sequencesTriangle: self-converse semigroups of order n with k idempotents.at n=28A058118Triangle read by rows: T(n,k) is the number of embeddings on the sphere of planar graphs with n vertices and k faces having connectivity exactly 2 and minimum vertex degree at least 3, k=6..2n-5.at n=50A378077