196573domain: NAppears in sequencesa(n) = T(n,n), T given by A026568. Also a(n) = number of integer strings s(0),...,s(n) counted by T, such that s(n)=0.at n=15A026569a(n) = 3*(2^n-1) - 2*n.at n=16A050488Expansion of (1-x)^(-1)/(1 - x - 2*x^2 + 2*x^3).at n=30A077866a(n) = 6*2^n - 2*n - 5.at n=15A142964