1572823domain: NAppears in sequencesa(n) = 3*(2^n-1) - 2*n.at n=19A050488Expansion of (1-x)^(-1)/(1 - x - 2*x^2 + 2*x^3).at n=36A077866a(n) = 6*2^n - 2*n - 5.at n=18A142964