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 A217291 Permutation of natural numbers arising from applying the walk of right triangular type-1 spiral (defined in A214230) to the data of square spiral (e.g. A214526). 0
 1, 2, 4, 16, 5, 6, 7, 8, 9, 10, 27, 11, 3, 15, 35, 63, 36, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 51, 84, 52, 28, 12, 14, 34, 62, 98, 142, 99, 64, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 83, 124, 173, 125, 85, 53, 29, 13, 33, 61, 97, 141, 193, 253 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..67. 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) 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, 1) # up walk2( 1, 1, -1, 0) # right-down if posX==SIZE-1: break walk2(-1, 0, 0, -1) # left CROSSREFS Cf. A214230, A214526, A217010. Sequence in context: A097542 A277850 A332352 * A364247 A338839 A350554 Adjacent sequences: A217288 A217289 A217290 * A217292 A217293 A217294 KEYWORD nonn AUTHOR Alex Ratushnyak, Sep 30 2012 STATUS approved

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Last modified March 1 17:12 EST 2024. Contains 370442 sequences. (Running on oeis4.)