This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
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
grid2 = [0] * (SIZE*SIZE)
posY = SIZE//2
posX = posY+1
grid2[posY*SIZE+posX-1] = grid2[posY*SIZE+posX] = 1
print(1, end=',')
def walk2(stepX, stepY, chkX, chkY):
global posX, posY
while 1:
a = grid[posY*SIZE+posX]
if a==0:
raise ValueError
print(a, end=',')
posX+=stepX
posY+=stepY
grid2[posY*SIZE+posX]=1
if grid2[(posY+chkY)*SIZE+posX+chkX]==0:
return
while posX!=SIZE-1:
walk2(-1, 1, -1, -1) # down-left
walk2(-1, -1, 1, -1) # up-left
walk2( 1, -1, 1, 0) # up-right
walk2( 1, 0, 1, 1) # right
walk2( 1, 1, -1, 1) # down-right
#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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