function A = lehmer(n) % % A matrix generator for iterative templates tester. % % LEHMER A = LEHMER(N) is the symmetric positive definite N-by-N matrix with % A(i,j) = i/j for j>=i. % A is totally nonnegative. INV(A) is tridiagonal, and explicit % formulas are known for its entries. % N <= COND(A) <= 4*N*N. % % References: % M. Newman and J. Todd, The evaluation of matrix inversion % programs, J. Soc. Indust. Appl. Math., 6 (1958), pp. 466-476. % Solutions to problem E710 (proposed by D.H. Lehmer): The inverse % of a matrix, Amer. Math. Monthly, 53 (1946), pp. 534-535. % % ============================================================================ A = ones(n,1)*(1:n); A = A./A'; A = tril(A) + tril(A,-1)'; % ------------ % End lehmer.m % ------------ .