140454

Appears in sequences

• Number of permutations in S_n avoiding {bar 5}2143 (i.e., every occurrence of 2143 is contained in an occurrence of a 52143).at n=9A137545
• Number of perfect matchings in the twisted graph (C_4 X C_n)_{(13)(24)}.at n=8A220868
• a(n) is the number of perfect matchings of an edge-labeled 2 X n Klein bottle grid graph, or equivalently the number of domino tilings of a 2 X n Klein bottle grid. (The twist is on the length-n side.)at n=17A351635