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 A217014 Permutation of natural numbers arising from applying the walk of a square spiral (e.g. A214526) to the data of triangular horizontal-last spiral (defined in A214226). 2
 1, 7, 22, 8, 2, 3, 4, 6, 20, 42, 21, 44, 75, 45, 23, 9, 11, 12, 13, 14, 15, 5, 19, 41, 71, 109, 72, 43, 74, 113, 160, 114, 76, 46, 24, 10, 28, 29, 30, 31, 32, 33, 34, 16, 18, 40, 70, 108, 154, 208, 155, 110, 73, 112, 159, 214 (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 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 1:     walk(1,  1, -1,  0)    # down-right     walk(-1, 0,  1, -1)    # left     walk(-1, 0,  1, -1)    # left     if posX<2:         break     walk(1, -1,  1,  1)    # up-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, A214226, A217010. Sequence in context: A082826 A130740 A101119 * A200886 A070412 A286572 Adjacent sequences:  A217011 A217012 A217013 * A217015 A217016 A217017 KEYWORD nonn,easy AUTHOR Alex Ratushnyak, Sep 23 2012 STATUS approved

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Last modified May 25 04:50 EDT 2019. Contains 323539 sequences. (Running on oeis4.)