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 A217015 Permutation of natural numbers arising from applying the walk of a square spiral (e.g. A214526) to the data of rotated-square spiral (defined in A215468). 4
 1, 5, 6, 2, 8, 3, 10, 4, 12, 24, 13, 14, 27, 15, 7, 17, 31, 18, 9, 20, 35, 21, 11, 23, 39, 59, 40, 25, 26, 43, 64, 44, 28, 16, 30, 48, 70, 49, 32, 19, 34, 53, 76, 54, 36, 22, 38, 58, 82, 110, 83, 60, 41, 42, 63, 88, 117, 89, 65, 45, 29, 47, 69, 95, 125, 96, 71, 50 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS PROG (Python) SIZE = 33       # must be 4k+1 grid = [0] * (SIZE*SIZE) posX = posY = SIZE//2 grid[posY*SIZE+posX]=1 posX += 1 grid[posY*SIZE+posX]=2 n = 3 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!=SIZE-1:     walk(-1,  1, -1, -1)    # down-left     walk(-1, -1,  1, -1)    # up-left     walk( 1, -1,  1,  0)    # up-right     walk( 1,  0,  1,  1)    # right     walk( 1,  1, -1,  1)    # down-right 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,     posX+=stepX     posY+=stepY     grid2[posY*SIZE+posX]=1     if grid2[(posY+chkY)*SIZE+posX+chkX]==0:         return while 1:     walk2(0, -1, 1, 0)    # up     walk2(1, 0, 0, 1)     # right     walk2(0, 1, -1, 0)    # down     walk2(-1, 0, 0, -1)   # left CROSSREFS Cf. A090861, A214526, A215468, A217010. Sequence in context: A038690 A154801 A253094 * A107825 A201332 A049253 Adjacent sequences:  A217012 A217013 A217014 * A217016 A217017 A217018 KEYWORD nonn,easy AUTHOR Alex Ratushnyak, Sep 23 2012 STATUS approved

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Last modified April 11 15:49 EDT 2021. Contains 342886 sequences. (Running on oeis4.)