A finite or infinite square matrix with rational entries. (If the matrix is infinite, all but a finite number of entries in each row must be 0.) The sum or product of two Bohr matrices is another Bohr matrix.
Bohr Matrix
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References
Apostol, T. M. "Bohr Matrices." §8.4 in Modular Functions and Dirichlet Series in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 167-168, 1997.Referenced on Wolfram|Alpha
Bohr MatrixCite this as:
Weisstein, Eric W. "Bohr Matrix." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BohrMatrix.html