38860021041domain: NAppears in sequencesExpansion of (1 - x)^(-1)/(1 + 2*x - 2*x^2 + x^3).at n=24A077918Number of length n+3 0..2 arrays with no four elements in a row with pattern abab (with a!=b) and new values 0..2 introduced in 0..2 order.at n=21A243038