A biquadrate number (or just biquadrate) is a number which can be expressed as the fourth power of an integer.
The sequence of positive biquadrates begins:
- $1, 16, 81, 256, 625, 1297, 2401, 4096, 6561, 10000, \ldots$
This sequence is A000583 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008).
The term biquadrate is archaic, deriving from the concept of a square of a square.