Pi-heptomino (or pi; sometimes called blasting cap at MIT after its shape at generation 1) is a common heptomino that stabilizes at generation 173, leaving behind six blocks, five blinkers and two ponds. The name "pi" is also applied to some slight variations of this object that follow that same evolutionary sequence – in a pi ship, for example, the pi-heptomino itself never actually arises. Forms that are synonymous with the pi-heptomino are displayed below.
In April 1992, Bill Gosper discovered that two blocks can be used to eat a pi, as shown below. The eating reaction takes 65 generations to complete. Gosper also discovered in the same month that a pi, along with two blocks and two blinkers, can be used to create a queen bee shuttle.
Generation 1 of pi-heptomino
A grandparent (a pentaplet) and parent (a hexomino) of pi
An alternative parent
of generation 1
This pattern, which resembles the word "Pi", evolves exactly like the Pi-heptomino after two generations, stabilizing at generation 174.