Click regio-count: thermal Huisgen 2 / CuAAC 1 ⇒ ratio 2

Sympy-exact witness of the CuAAC-vs-Huisgen regio-selectivity count. Setup: thermal Huisgen 1,3-dipolar cycloaddition of azide + terminal-alkyne yields both 1,4- and 1,5-disubstituted 1,2,3-triazoles (2 regio-isomers, typically ~1:1 ratio…