A217014 -id:A217014 - cp's OEIS frontend

A217295 Permutation of natural numbers arising from applying the walk of triangular horizontal-last spiral (defined in A214226) to the data of square spiral (e.g. A214526).

1, 5, 6, 7, 22, 8, 2, 4, 16, 36, 17, 18, 19, 20, 21, 44, 75, 45, 23, 9, 11, 3, 15, 35, 63, 99, 64, 37, 38, 39, 40, 41, 42, 43, 74, 113, 160, 114, 76, 46, 24, 10, 28, 12, 14, 34, 62, 98, 142, 194, 143, 100, 65, 66, 67, 68, 69, 70, 71, 72, 73, 112, 159, 214, 277

Offset: 1

Alex Ratushnyak, Sep 30 2012

nonn

Cf. A214226, A214526, A217014.

SIZE = 29    # 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:
    walk(0, -1, 1, 0)    # up
    walk(1, 0, 0, 1)     # right
    walk(0, 1, -1, 0)    # down
    walk(-1, 0, 0, -1)   # left
import sys
grid2 = [0] * (SIZE*SIZE)
posX = posY = SIZE//2
grid2[posY*SIZE+posX]=1
def walk2(stepX, stepY, chkX, chkY):
  global posX, posY
  while 1:
    a = grid[posY*SIZE+posX]
    if a==0:
        sys.exit(1)
    print(a, end=', ')
    posX+=stepX
    posY+=stepY
    grid2[posY*SIZE+posX]=1
    if grid2[(posY+chkY)*SIZE+posX+chkX]==0:
        return
while 1:
    walk2(1,  1, -1,  0)    # down-right
    walk2(-1, 0,  1, -1)    # left
    walk2(-1, 0,  1, -1)    # left
    if posX<2:
        break
    walk2(1, -1,  1,  1)    # up-right

A220102 Permutation of natural numbers arising from applying the walk of square spiral (e.g. A214526) to the data of double square spiral (defined in A220098).

Original entry on oeis.org

1, 2, 4, 6, 8, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 50, 52, 54, 56

Offset: 1

Alex Ratushnyak, Dec 04 2012

nonn

Cf. A214526, A220098, A217010, A217011, A217012, A217013, A217014, A217015.

#include 
#define SIZE 20
int grid[SIZE][SIZE];
int direction[] = {0, -1,  1, 0, 0, 1, -1, 0};
main() {
  int i, j, x1, y1, x2, y2, stepSize;
  int direction1pos=0, direction2pos=4, val;
  x1 = y1 = x2 = y2 = SIZE/2;
  for (val=grid[y1][x1]=1, stepSize=0; ; ++stepSize) {
    if (x1<1 || x1>=SIZE-1 || x2<1 || x2>=SIZE-1) break;
    if (y1<1 || y1>=SIZE-1 || y2<1 || y2>=SIZE-1) break;
    for (i=stepSize|1; i; ++val,--i) {
      x1 += direction[direction1pos  ];
      y1 += direction[direction1pos+1];
      x2 += direction[direction2pos  ];
      y2 += direction[direction2pos+1];
      grid[y1][x1] = val*2;
      grid[y2][x2] = val*2+1;
    }
    direction1pos = (direction1pos+2) & 7;
    direction2pos = (direction2pos+2) & 7;
  }
  direction1pos=0;
  x1 = y1 = SIZE/2;
  for (stepSize=2; ; ++stepSize) {
    for (i=stepSize/2; i; --i) {
      if (grid[y1][x1]==0) return;
      printf("%d, ",grid[y1][x1]);
      x1 += direction[direction1pos  ];
      y1 += direction[direction1pos+1];
    }
    direction1pos = (direction1pos+2) & 7;
  }
}

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A217295 Permutation of natural numbers arising from applying the walk of triangular horizontal-last spiral (defined in A214226) to the data of square spiral (e.g. A214526).

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