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Search: id:A049319
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| A049319 |
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Number of 3-dimensional integer direction vectors (a,b,c) towards grid points at squared integer distance 2n-1. |
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+0
3
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| 6, 24, 24, 48, 72, 72, 72, 96, 96, 120, 192, 144, 120, 216, 168, 192, 288, 192, 216, 288, 240, 264, 288, 288, 336, 384, 312, 288, 480, 360, 360, 576, 288, 408, 576, 432, 432, 480, 576, 648, 504, 384, 672, 528, 576, 768, 480, 576, 864, 600, 624
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A vector is a direction vector if its nonzero components have their GCD = 1.
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EXAMPLE
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The 4 directions towards points at squared distance 29 (i.e. for n=15) are (signed permutations of) [ 24,16,3 ],[ 24,12,11 ],[ 21,20,0 ],[ 21,16,12 ]
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CROSSREFS
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Cf. A049318, A049317.
Sequence in context: A052697 A029592 A112034 this_sequence A072710 A069235 A118372
Adjacent sequences: A049316 A049317 A049318 this_sequence A049320 A049321 A049322
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KEYWORD
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nonn
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AUTHOR
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(wouter.meeussen(AT)pandora.be)
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