[iswzbowh] Pi controversies

The Greek letter pi is involved in two mathematical controversies.

Lowercase pi is pitted against the one legged lowercase tau as the constant describing the circle.

Uppercase pi is pitted against one legged uppercase gamma as the continuous extension of the factorial function.

Vaguely relatedly, uppercase pi signifying product lives in harmony with uppercase sigma signifying sum.  Similarly lowercase pi and sigma for molecular electron orbitals.