> coffee spiral.coffee

----Spiral n=6
[ [ 0, 1, 2, 3, 4, 5 ],
  [ 19, 20, 21, 22, 23, 6 ],
  [ 18, 31, 32, 33, 24, 7 ],
  [ 17, 30, 35, 34, 25, 8 ],
  [ 16, 29, 28, 27, 26, 9 ],
  [ 15, 14, 13, 12, 11, 10 ] ]

----Spiral n=7
[ [ 0, 1, 2, 3, 4, 5, 6 ],
  [ 23, 24, 25, 26, 27, 28, 7 ],
  [ 22, 39, 40, 41, 42, 29, 8 ],
  [ 21, 38, 47, 48, 43, 30, 9 ],
  [ 20, 37, 46, 45, 44, 31, 10 ],
  [ 19, 36, 35, 34, 33, 32, 11 ],
  [ 18, 17, 16, 15, 14, 13, 12 ] ]