Vyxal, 28 bytes ⇧Þ□λ÷N^›WDṘ²+^∑1<i;ÞZÞḋIRf⁰i Try it Online! Based on @Arnauld's Javascript answer. How? λ÷N^›WDṘ²+^∑1<i; - find the (i, j)th entry of the matrix λ ; - lambda STACK (top ->) ÷ - unwrap i j N - negate i -j ...
Seggan/Fig