Trimorphic Number
A number 
such that the last digits of 
are the same as . 49 is trimorphic since 
(Wells 1986,p. 124). The first few are 1, 4, 5, 6, 9, 24, 25, 49, 51, 75, 76, 99, 125, 249, 251, 375, 376, 499, ... (Sloane's A033819).
References
Sloane, N. J. A. Sequence A033819in ``The On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html. Wells, D. The Penguin Dictionary of Curious and Interesting Numbers. Middlesex, England: Penguin Books, 1986.
- Wallace-Bolyai-Gerwein Theorem
- Wallace-Simson Line
- Wallis Cosine Formula
- Wallis Formula
- Wallis's Conical Edge
- Wallis Sieve
- Wallis Sine Formula
- Wallis's Problem
- Wallpaper Groups
- Walsh Function
- Walsh Index
- Wang's Conjecture
- Ward's Primality Test
- Waring Formula
- Waring's Conjecture
- Waring's Prime Conjecture
- Waring's Problem
- Waring's Sum Conjecture
- Waring's Theorem
- Watchman Theorem
- Watson-Nicholson Formula
- Watson Quintuple Product Identity
- Watson's Formula
- Watson's Theorem
- Watt's Curve