4370620275domain: NAppears in sequencesNumber of permutations in S_n avoiding the strings 123, 321 and 231.at n=21A060696Sum of product of odd numbers <= n and the product of even numbers <= n.at n=19A076051Product of first n odd numbers plus product of first n even numbers: (2n-1)!! + (2n)!!, where k!! = A006882(k).at n=9A232617