# New in *MathWorld* -- April
2002

### Tuesday April 30, 2002

- Catalan Number (modified)
- Derivative (modified)
- Discrete Fourier Transform (modified)
- Double Series (modified)
- Dyck Path (modified)
- Epimorphism (modified)
- Generating Function (modified)
- Greatest Common Divisor (modified)
- Hofstadter's Q-Sequence (modified)
- Injection (modified)
- Limit (modified)
- Marienbad (modified)
- Monomorphism (modified)
- Nim (modified)
- Nim-Heap (modified)
- Numerical Differentiation
- Quotient Group (modified)
- Staircase Walk (modified)
- Subfactorial (modified)
- Surjection (modified)

### Monday April 29, 2002

- Bennequin's Conjecture (modified)
- Combination Lock (modified)
- Hofstadter-Conway $10,000 Sequence (modified)
- Integer Polynomial (modified)
- Logarithmic Integral (modified)
- Riemann Zeta Function (modified)
- Self-Counting Sequence (modified)
- Slice-Bennequin Inequality

### Sunday April 28, 2002

- Bernoulli Number (modified)
- Butterfly Function
- Linear Algebra (modified)
- Munching Squares
- OR (modified)
- Pythagoras's Constant (modified)
- Riemann Zeta Function (modified)
- Sierpiński Sieve (modified)
- Square Root (modified)
- Square Root Algorithms
- XOR (modified)

### Saturday April 27, 2002

- 196-Algorithm (modified)
- Cyclotomic Polynomial (modified)
- Dual Scalar (modified)
- Euler-Mascheroni Constant (modified)
- Gauss's Polynomial Theorem (modified)
- Hofstadter-Conway $10,000 Sequence (modified)
- Integer Polynomial (modified)
- Least Significant Bit
- Polar Vector
- Polylogarithm (modified)
- Positive Integer (modified)
- Principle of Strong Induction (modified)
- Principle of Weak Induction (modified)
- Pseudovector (modified)
- Reverse-Then-Add Sequence (modified)
- Riemann Zeta Function (modified)
- Self-Counting Sequence
- Sort-Then-Add Sequence (modified)
- Super Catalan Number (modified)
- Unsolved Problems (modified)
- Vector (modified)

### Friday April 26, 2002

- Butterfly Curve (modified)
- Cubical Parabolic Hyperbola (modified)
- Fair Game (modified)
- Golden Ratio (modified)
- Hadamard Product
- Marienbad
- Misère-Form Game
- Nim-Value (modified)
- Normal-Form Game
- Quadrifolium (modified)
- Quadruple Point (modified)
- Singleton Graph (modified)
- Unfair Game (modified)
- Wallis Cosine Formula (modified)
- Wallis Sine Formula (modified)
- Weierstrass Factor Theorem (modified)
- Weierstrass Product Theorem (modified)
- Weierstrass's Theorem (modified)

### Thursday April 25, 2002

- Biotic Potential
- Butterfly Curve (modified)
- Exact First-Order Ordinary Differential Equation
- Linear Recurrence Equation
- Marcum Q-Function
- Partial Differential Equation (modified)
- Quadratic Recurrence Equation
- Recurrence Equation
- Recurrence Relation (modified)
- Second-Order Ordinary Differential Equation

### Wednesday April 24, 2002

- Cofree Module
- Partition (modified)
- Partition Function q (modified)
- Stirling Number of the Second Kind (modified)
- Wallis Formula (modified)

### Tuesday April 23, 2002

- Collatz Problem (modified)
- Empty Graph (modified)
- Euler-Mascheroni Constant (modified)
- Fractional Part (modified)
- Fraser's Spiral (modified)
- Free Module
- Nonempty Set (modified)
- Partition Function P (modified)
- Sine (modified)
- Singleton Function
- Singleton Graph
- Singleton Set
- Unsolved Problems (modified)
- Zero Module
- Zero Ring

### Monday April 22, 2002

- Almost Integer (modified)
- Binary (modified)
- Frieze Group
- Quaternary (modified)
- Roundoff Error (modified)
- Solved Problems
- Substitution System (modified)
- Such That
- Ternary (modified)
- Unsolved Problems (modified)
- Wallpaper Groups (modified)

### Sunday April 21, 2002

- Fraser's Spiral
- Golomb Ruler (modified)
- Matrix Multiplication (modified)
- Orthogonal Matrix (modified)
- Similarity Transformation (modified)
- String Figure

### Saturday April 20, 2002

- Condition Number (modified)
- Riemann Zeta Function (modified)

### Friday April 19, 2002

- Café Wall Illusion
- Laplace Transform (modified)
- Triangle Wave

### Thursday April 18, 2002

- Prime Spiral (modified)

### Wednesday April 17, 2002

- Conjunction (modified)
- Conjunctive Normal Form (modified)
- Disjunction (modified)
- Disjunctive Normal Form (modified)
- Multiple Root (modified)
- Statement Form
- Statement Letter

### Tuesday April 16, 2002

- Abelian Extension (modified)
- Extension Field (modified)
- Field Automorphism
- Fundamental Theorem of Galois Theory
- Galois Extension Field (modified)
- Geodesic (modified)
- Multiple Root (modified)
- Normal Extension
- Normal Form (modified)
- Perfect Field
- Purely Inseparable Extension
- Root of Unity (modified)
- Separable Extension
- Separable Polynomial
- Split
- Splitting Field (modified)
- Transcendence Degree

### Friday April 12, 2002

### Thursday April 11, 2002

- Differential Evolution (modified)
- Nelder-Mead Method (modified)
- Simulated Annealing (modified)
- Totalistic Cellular Automaton (modified)

### Wednesday April 10, 2002

### Tuesday April 9, 2002

- Elementary Cellular Automaton (modified)
- Newton-Girard Formulas (modified)
- Poincaré Conjecture (modified)
- Spinor (modified)
- Spinor Field
- Twistor Equation

### Monday April 8, 2002

- Abstract Vector Space
- Chess (modified)
- Contractible
- Elevator Paradox (modified)
- Fibonacci Q-Matrix (modified)
- Homotopy Type
- Translate (modified)
- Vieta's Formulas

### Sunday April 7, 2002

- Casting Out Nines (modified)
- Coincident Lines
- Intersecting Lines
- Midy's Theorem (modified)
- Quadratic Curve (modified)

### Saturday April 6, 2002

- Cubic Formula (modified)

### Friday April 5, 2002

- Arithmetic Mean (modified)
- Bernoulli Polynomial (modified)
- Chess (modified)
- Functional Derivative (modified)
- Normal Distribution (modified)
- Percolation Threshold (modified)
- Quartic Equation (modified)

### Thursday April 4, 2002

- Bilateral Laplace Transform
- Chebyshev Polynomial of the Second Kind (modified)
- Closed Sentential Formula (modified)
- Laplace Transform (modified)
- Open Sentential Formula (modified)
- Unilateral Laplace Transform

### Tuesday April 2, 2002

- Eternity (modified)
- Fermat-Catalan Conjecture (modified)
- Pauli Matrices (modified)
- Translate
- Triangular Number (modified)

### Monday April 1, 2002

- Ceiling Function (modified)
- Cylindrical Segment (modified)
- Euler-Mascheroni Constant (modified)
- Floor Function (modified)
- Hexagonal Pyramid (modified)
- Integer Part (modified)
- Königsberg Bridge Problem (modified)
- Nearest Integer Function (modified)
- Twin Prime Cluster (modified)

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