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 A214252 Sum of the eight nearest neighbors of n in a right triangular type-3 spiral with positive integers. 5
 62, 88, 63, 89, 76, 102, 170, 127, 126, 152, 223, 159, 140, 139, 159, 221, 175, 171, 179, 202, 249, 353, 274, 252, 254, 262, 279, 323, 430, 330, 293, 283, 291, 299, 307, 336, 425, 352, 339, 347, 355, 363, 371, 403, 468, 608, 493, 453, 446, 454, 462, 470, 478, 504 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Right triangular type-1 spiral (A214230): implements the sequence Up, Right-down, Left. Right triangular type-2 spiral (A214251): Left, Up, Right-down. Right triangular type-3 spiral: Right-down, Left, Up. LINKS EXAMPLE Right triangular type-3 spiral begins: 78 77  46 76  45  47 75  44  22  48 74  43  21  23  49 73  42  20   7  24  50 72  41  19   6   8  25  51 71  40  18   5   1   9  26  52 70  39  17   4   3   2  10  27  53 69  38  16  15  14  13  12  11  28  54 68  37  36  35  34  33  32  31  30  29  55 67  66  65  64  63  62  61  60  59  58  57  56 The eight nearest neighbors of 5 are 1, 3, 4, 17, 18, 19, 6, 8. Their sum is a(5)=76. PROG (Python) SIZE=28  # must be even grid = [0] * (SIZE*SIZE) saveX = [0]* (SIZE*SIZE) saveY = [0]* (SIZE*SIZE) saveX[1] = saveY[1] = 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     saveX[n]=posX     saveY[n]=posY     n+=1     if posY==0 or grid[(posY+chkY)*SIZE+posX+chkX]==0:         return while posY!=0:     walk( 1, 1, -1,  0)    # right-down     walk(-1, 0,  0, -1)    # left     walk(0, -1,  1,  1)    # up for n in range(1, 92):     posX = saveX[n]     posY = saveY[n]     k = grid[(posY-1)*SIZE+posX] + grid[(posY+1)*SIZE+posX]     k+= grid[(posY-1)*SIZE+posX-1] + grid[(posY-1)*SIZE+posX+1]     k+= grid[(posY+1)*SIZE+posX-1] + grid[(posY+1)*SIZE+posX+1]     k+= grid[posY*SIZE+posX-1] + grid[posY*SIZE+posX+1]     print k, CROSSREFS Cf. A214230. Cf. A214251. Sequence in context: A043994 A039479 A118156 * A282241 A114966 A104078 Adjacent sequences:  A214249 A214250 A214251 * A214253 A214254 A214255 KEYWORD nonn,easy AUTHOR Alex Ratushnyak, Jul 08 2012 STATUS approved

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Last modified September 23 16:41 EDT 2020. Contains 337315 sequences. (Running on oeis4.)