140680domain: NAppears in sequencesNumber of bifix-free (or primary, or unbordered) words of length n over a two-letter alphabet.at n=19A003000Number of partitions of n objects of 2 colors with parts size >1.at n=21A060285Number of length-n binary words having no nontrivial prefix that is a palindrome of odd length.at n=18A308528