963270domain: NAppears in sequencesExpansion of 2*(1-x)*(2*x^2+4*x+1) / (1-x-x^2)^2.at n=21A271786Integers x such that there exist two integers 0<x<=y<=z such that psi(x) = psi(y) = psi(z) = x + y + z.at n=31A385852Integers y such that there exist two integers 0<x<=y<=z such that psi(x) = psi(y) = psi(z) = x + y + z.at n=27A386901