A217013 Permutation of natural numbers arising from applying the walk of a square spiral (e.g. A214526) to the data of triangular horizontal-first spiral (defined in A214250).

1, 3, 14, 4, 6, 7, 8, 2, 12, 30, 13, 32, 59, 33, 15, 5, 19, 20, 21, 22, 23, 9, 11, 29, 55, 89, 56, 31, 58, 93, 136, 94, 60, 34, 16, 18, 40, 41, 42, 43, 44, 45, 46, 24, 10, 28, 54, 88, 130, 180, 131, 90, 57, 92, 135, 186, 245, 187, 137, 95, 61, 35, 17, 39, 69

Offset: 1

Author

Alex Ratushnyak, Sep 23 2012

Keywords

• nonn
• easy

Crossrefs

Cf. A090861, A214526, A214250, A217010.

Programs

Python

SIZE = 33       # must be 4k+1
grid = [0] * (SIZE*SIZE)
posX = posY = SIZE//2
grid[posY*SIZE+posX]=1
n = 2
def walk(stepX, stepY, chkX, chkY):
  global posX, posY, n
  while 1:
    posX+=stepX
    posY+=stepY
    grid[posY*SIZE+posX]=n
    n+=1
    if grid[(posY+chkY)*SIZE+posX+chkX]==0:
        return
while posX