For an Integer , let
denote the Least Prime Factor of , i.e., the number in
the factorization

with for . For , 3, ..., the first few are 2, 3, 2, 5, 2, 7, 2, 3, 2, 11, 2, 13, 2, 3, ... (Sloane's A020639). The above plot of the least prime factor function can be seen to resemble a jagged terrain of mountains, which leads to the appellation of ``Twin Peaks'' to a Pair of Integers such that

- 1. ,
- 2. ,
- 3. For all , Implies .

**References**

Sloane, N. J. A. A020639 and A046027 in ``An On-Line Version of the Encyclopedia of Integer Sequences.'' http://www.research.att.com/~njas/sequences/eisonline.html.

© 1996-9

1999-05-26