themes

shapes with paper

origami butterflies, paper rhombic hexecontrahedron,paper rhombic triacontrahedron, edge colored icosahedron, origami cup, origami frog, knot tiles, window patterns, silver rectangle window patterns, spherical tetrahedron, origami envelope, more about the origami envelope,

water bomb tessellation, simple sonobe handout, an origami workshop

shapes with numbers

polygonal numbers, mandelbrot set,
 finding polygonal numbers in multiplication tables, 

lucas number triangle, catalan number triangle, 

harmonic denominator triangle, euler's number triangle, 

something surprising in pascal's triangle,
tesseracts and factors, frames and octahedrals,
triangular games, triangle of triangles

chess-related

knight's path puzzles, king's path puzzles, more knight's tour puzzles,

 knight moves, closing knight's tours, punctured tours

spirals

spiral drawings, sequences on number spirals, polygonal numbers on spirals

phyllotaxis, primes on a log spiral, hypocycloid scrambler and scrambler fractal
triskelion spiral, euler spirals

book reviews, other ramblings

review of Mathema, mathematics of ancient Iraq,
the best mathematics writing of 2011, mere calculation,
the math humor of Stephen Leacock,  

math as a tree, old math books, mathematics and friendship,
species and culture of mathematics,jump math, halmos aphorisms,
Ludwig's thought experiment, The Puzzle Universe

things from school

means and trig ratios, polygons and multiplication, 

polynomial division: the grid method,
multiplication table rainbows, grade one functions,
how to learn math, old math curriculum,
generic rectangles, backwards reverse division
a prime sieve

logic puzzles

liars and truthers, accusation graphs, triangle games

  geometric designs

tilings with dented polygons and rhombs,
simple designs, envelope doodles, bipartite graphs,
drawing labyrinths, modulo-phyllo, knot tiles,
square iterations, fused polygons, sliced polygons, more fused polygons,
rings of polygons, rotating knots

fractals, etc.

Mandelbrot set, a fractal family, animated iterations in GSP,
scrambler fractal, Catalan number triangle fractal, Ford Circles in Fathom,
Pascal Triangle in TinkerPlots, Random Walks in Fathom, hex life and sandpiles,
GSP snowflakes