Let  be the set of all sequences that contain all sequences  where  and all other , and define

Then the merit factor problem requires the minimization of  over  for a fixed .

For , 2, ..., the first few minima are 5, 10, 18, 27, 43, 52, 72, ... (OEIS A091386).

This problem is known to be very hard, but is not known to be in one of the recognized combinatorial classes like NP (Borwein and Bailey 2003, p. 6).

REFERENCES:

Borwein, J. and Bailey, D. Mathematics by Experiment: Plausible Reasoning in the 21st Century. Wellesley, MA: A K Peters, 2003.

Borwein, P. B. Computational Excursions in Analysis and Number Theory. New York: Springer-Verlag, 2002.

Sloane, N. J. A. Sequence A091386 in "The On-Line Encyclopedia of Integer Sequences."