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 A217296 Permutation of natural numbers arising from applying the walk of rotated-square spiral (defined in A215468) to the data of square spiral (e.g. A214526). 2
 1, 4, 6, 8, 2, 3, 15, 5, 19, 7, 23, 9, 11, 12, 14, 34, 16, 18, 40, 20, 22, 46, 24, 10, 28, 29, 13, 33, 61, 35, 17, 39, 69, 41, 21, 45, 77, 47, 25, 27, 53, 54, 30, 32, 60, 96, 62, 36, 38, 68, 106, 70, 42, 44, 76, 116, 78, 48, 26, 52, 86, 87, 55, 31, 59, 95, 139 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS PROG (Python) 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) posY = SIZE//2 posX = posY+1 grid2[posY*SIZE+posX-1] = grid2[posY*SIZE+posX] = 1 print 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,     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 CROSSREFS Cf. A215468, A214526, A217015. Sequence in context: A181097 A206798 A200366 * A330154 A179371 A097455 Adjacent sequences:  A217293 A217294 A217295 * A217297 A217298 A217299 KEYWORD nonn,changed AUTHOR Alex Ratushnyak, Sep 30 2012 STATUS approved

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Last modified September 22 22:24 EDT 2020. Contains 337291 sequences. (Running on oeis4.)