Umbral calculus

In mathematics before the 1970s, the term umbral calculus referred to the surprising similarity between seemingly unrelated polynomial equations and certain shadowy techniques used to "prove" them. These techniques were introduced by John Blissard and are sometimes called Blissard's symbolic method.^[1] They are often attributed to Édouard Lucas (or James Joseph Sylvester), who used the technique extensively.^[2]