Erdős Problem #1131 — Minimum integrated squared Lagrange basis

For x1,…,xn∈[−1,1]x_1,\ldots,x_n\in [-1,1] let lk(x)=∏i≠k(x−xi)∏i≠k(xk−xi),l_k(x)=\frac{\prod_{i\neq k}(x-x_i)}{\prod_{i\neq k}(x_k-x_i)}, which are such that lk(xk)=1l_k(x_k)=1 and lk(xi)=0l_k(x_i)=0 for i≠ki\neq k. What is the minimal value of I(x1,…,xn)=∫−11∑k∣lk(x)∣2dx?I(x_1,\ldots,x_n)=\int_{-1}^1 \sum_k \lvert l_k(x)\rvert^2\mathrm{d}x? In particular, is it true that min⁡I=2−(1+o(1))1n?\min I =2-(1+o(1))\frac{1}{n}?

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