= Midpoint cubic spline collocation
{title2=$A_n=\tfrac16\operatorname{tridiag}(1,4,1)$}
Sampling consecutive <Cardinal cubic B-splines> at the centers of their supports gives diagonal values $2/3$ and adjacent values $1/6$, with all other values zero. Finite truncation gives the displayed <B-spline collocation matrix>, including its endpoint rows without wrapping or adding boundary conditions. Its inverse has alternating signs. The <exact inverse norm of midpoint cubic spline collocation> is less than three for each finite dimension and approaches three as the dimension grows.
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