44695552domain: NAppears in sequencesNumber of permutations of [ n ] with exactly one 132-pattern and two 123-patterns.at n=17A046718a(n) = 2^n*Lucas(n), where Lucas = A000032.at n=15A087131a(n) = A062401(2^n-1).at n=25A096853Expansion of 2*x*(1+4*x) / (1-12*x+16*x^2).at n=7A270445