Data:9 19/HOMFLYPT Polynomial

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle -z^2 a^4+z^4 a^2+z^2 a^2+a^2+z^4-2 z^2 a^{-2} - a^{-2} + a^{-4} }