Hofstadter G-Sequence
The sequence defined by 
and
The first few terms are 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, ... (Sloane's A005206).
References
Hofstadter, D. R. Gödel, Escher, Bach: An Eternal Golden Braid. New York: Vintage Books, p. 137, 1989. Sloane, N. J. A. SequenceA005206/M0436in ``An On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.
- Elliptic Paraboloid
- Elliptic Partial Differential Equation
- Elliptic Plane
- Elliptic Point
- Elliptic Pseudoprime
- Elliptic Rotation
- Elliptic Theta Function
- Elliptic Torus
- Elliptic Umbilic Catastrophe
- Ellison-Mendès-France Constant
- Elongated Cupola
- Elongated Dipyramid
- Elongated Dodecahedron
- Elongated Gyrobicupola
- Elongated Gyrocupolarotunda
- Elongated Orthobicupola
- Elongated Orthobirotunda
- Elongated Orthocupolarotunda
- Elongated Pentagonal Cupola
- Elongated Pentagonal Dipyramid
- Elongated Pentagonal Gyrobicupola
- Elongated Pentagonal Gyrobirotunda
- Elongated Pentagonal Gyrocupolarotunda
- Elongated Pentagonal Orthobicupola
- Elongated Pentagonal Orthobirotunda