I heart Euler Bumper Sticker

Leonhard Euler (1789-1857) was perhaps the most prolific mathematician in history: his collected papers fill over 70 volumes. This in spite of being blind for the last 17 years of his life (LabKitty looks at our tiny stack of publications, weeps). Said to have a prodigious memory, Euler apparently not only memorised trigonometric identities and prime numbers and digits of pi, but also the entire Aeneid in Latin (LabKitty tries to remember our PIN number, weeps). Here, we take the I-heart concept, and instead of a heart we used the greek symbol phi, which is generally associated with Euler's totient function.