Zinbiel algebras are the Koszul dual of algebras named for this mathematician. This mathematician’s namesake algebra is a noncommutative generalization of Lie algebra for which Engel’s theorem still hold. A formula of pi named for this European mathematician is sometimes also named for Madhava, (15[1])who discovered the more general “Gregory’s series” more than a century before. An entry of a construct named for this mathematician is equal to the entry diagonally above (-5[1])on the left minus the entry to the left; that construct is his namesake (*) harmonic triangle. The use of the symbol dx to represent an infinitesimal (10[1])change in x is this (10[1])mathematician’s namesake notation. For 10 points, identify this German mathematician, whose claim of having invented calculus was disputed by Isaac Newton. ■END■ (10[1])