Fountain
An 
fountain is an arrangement of 
coins in rows such that exactly 
coins are in the bottom row and eachcoin in the 
st row touches exactly two in the 
th row.
References
Berndt, B. C. Ramanujan's Notebooks, Part III. New York: Springer-Verlag, p. 79, 1985.
- Picard's Existence Theorem
- Picard's Little Theorem
- Picard's Theorem
- Picard Variety
- Pick's Formula
- Pick's Theorem
- Picone's Theorem
- Piecewise Circular Curve
- Pie Cutting
- Pigeonhole Principle
- Pi Heptomino
- Pillai's Conjecture
- Pilot Vector
- Pinching Theorem
- Pinch Point
- Pine Cone Number
- Piriform
- Pisot-Vijayaraghavan Constants
- Pistol
- Pitchfork Bifurcation
- Pivoting
- Pivot Theorem
- Pizza Theorem
- Place (Digit)
- Place (Field)