Zahlen / Numbers

• Was heißt hier prim?
• The period length of the decimal expansion of a fraction
• Computing the period length of a decimal expansion
• Das Geburtstagsrätsel
• The prime factors of 10⁴⁸⁶-1
• Solutions of Mordell's equation y² = x³ + k
• Potenzsummen, Bernoulli-Zahlen und Euler'sche Summenformel (pdf)
• Pi is irrational

Formale Sprachen / Formal languages

• Reguläre Sprachen, reguläre Ausdrücke
• Natural and formal languages – not worked out, only English fragments with German comments