278104domain: NAppears in sequencesNumbers of isomers of unbranched a-4-catapolypentagons - see Brunvoll reference for precise definition.at n=11A121136Number of compositions of 8*n into parts 7 and 8.at n=20A373913a(n) = Sum_{k=0..floor(4*n/7)} binomial(k,4*n-7*k).at n=40A392355