Critical parameters of N-vector spin models on 3d lattices from high temperature series extended to order beta²¹

High temperature expansions for the free energy, the susceptibility and the second correlation moment of the classical N-vector model [also denoted as the O(N) symmetric classical spin Heisenberg model or as the lattice O(N) nonlinear sigma model] have been extended to order beta^{21} on the simple cubic and the body centered cubic lattices, for arbitrary N. The series for the second field derivative of the susceptibility has been extended to order beta^{17}. An analysis of the newly computed series yields updated estimates of the model's critical parameters in good agreement with present renormalization group estimates.