174798domain: NAppears in sequencesNumber of permutations of length n which avoid the patterns 1234, 3142, 3421.at n=18A116767Triangle read by rows: numbers of isomers of unbranched a-4-catapolynonagons.at n=48A120650Unbranched a-4-catapolynonagons (see Brunvoll reference for precise definition).at n=6A121126