The story
Named after German mathematician Peter Gustav Lejeune Dirichlet (1805–1859).
Etymology from Wiktionary, CC BY-SA 4.0.
Dirichlet eta function
Today it means: The alternating sum of the Dirichlet series expansion of the Riemann zeta function:η(s)=∑ₙ₌₁ ᪲(-1)ⁿ⁻¹/nˢ=1/(1ˢ)-1/(2ˢ)+1/(3ˢ)-1/(4ˢ)+⋯. Full definition →