तस्य द्विरथोत्तरा वृद्धिरैकविंशतिरथादिति ॥ कZ_१०.५.१५ ॥
tasya dvirathottarā vṛddhir aikaviṃśatirathād iti
उस (समव्यूह) की वृद्धि दो-दो रथ जोड़कर होती है—इक्कीस रथों से आरम्भ करके।
Even-number increments preserve bilateral symmetry (left/right) and keep wings balanced while scaling the formation.
A minimum viable baseline size for this formation family, from which standardized expansions are authorized.