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Search: id:A049317
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| A049317 |
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Number of 3-dimensional integer direction vectors (a,b,c) towards grid points at squared integer distance 2n-1 with a >= b >= c >= 0. |
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+0
3
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| 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 4, 3, 3, 5, 4, 4, 7, 4, 5, 6, 6, 6, 6, 6, 7, 9, 7, 6, 11, 8, 8, 12, 7, 9, 12, 9, 10, 10, 12, 10, 14, 11, 9, 14, 12, 12, 16, 10, 13, 19, 13, 13, 16, 14, 14, 18, 15, 12, 18, 16, 17, 21, 13, 16, 23, 17, 20, 18, 18, 18, 24, 18, 15, 28, 19, 19, 25
(list; graph; listen)
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OFFSET
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1,5
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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, A049319.
Sequence in context: A032229 A024366 A140682 this_sequence A134544 A106161 A105588
Adjacent sequences: A049314 A049315 A049316 this_sequence A049318 A049319 A049320
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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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