Contents
Editorial		1
Articles
Difference equations, determinants and the Secret Santa problem	Tony Ward	2
Mathematical operators and ways of reasoning	David Ginat	7
Partitions of primes and other sequences	K. Robin McLean	15
The discovery of two new magic knight's tours	Tim S. Roberts	22
The tiling conjecture for equiangular polygons	K. Robin McLean	28
Matter for Debate
Readers respond		35
Notes 89.01 to 89.27
Perfect, and almost perfect, Pythagorean triangles	Philip Maynard	36
Some obvious facts about the primes?	Martin Griffiths	39
A result on the sequence of primes	Panagiotis T. Krasopoulos	41
An extremum for  where  and  are constant	Roy Barbara	43
Proof without words	Hung-Ping Tsao	46
Instant unitary matrices	Ladislav Beran	46
An integral for the careless mathematician	Martin Griffiths	47
The crossed ladder problem	Manfred Ritter	50
The integral	Ll. G. Chambers	52
Convergents to  via the Farey mean?	Martin Griffiths	54
Relations between Euler's constant, Riemann's zeta function and Bernoulli numbers	Hwang Chien-Lih	57
A moments of inertia proof of Euler's formula for	Nick Lord	59
More on railway station arches	Norman Routledge	60
Back to the Euler line	J. A. Scott	65
Yet more heuristics	J. A. Scott	68
A polygon inequality	John Melville	68
Flexible quadrilaterals	A. F. Beardon	71
Converse of a property of right triangles	Gyula Darvasi	72
Calculations on face and vertex regular polyhedra	Udaya Chinthaka Jayatilake	76
A property of rectangles	Michael O'Loughlin	81
Incircles of right-angled triangles	Robert J. Clarke	82
Generalised Lucas circles of a cyclic quadrilateral	Fukuzo Suzuki	86
The lemniscate of Bernoulli	H. Martyn Cundy	89
A nine-point hyperbola	J. A. Scott	93
On the tetrahedron inequality	J. A. Scott	96
Construction of Pythagorean magic squares	Emanuel Emanouilidis	99
What's the quickest route from  to ?	Stuart Simons	101
Feedback		104
Problem Corner	Nick Lord	115
Student Problems	Tim Cross	120
Reviews		123

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