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Search: id:A049318
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| A049318 |
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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 >= 0, b >= 0, c >= 0. |
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3
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| 3, 3, 6, 6, 9, 9, 12, 12, 15, 15, 24, 18, 18, 27, 24, 24, 36, 24, 30, 36, 33, 33, 36, 36, 42, 48, 42, 36, 60, 45, 48, 72, 42, 51, 72, 54, 57, 60, 72, 60, 81, 63, 54, 84, 69, 72, 96, 60, 75, 108, 78, 96, 81, 84, 108, 87, 72, 108, 96, 99, 120, 78, 96, 132, 99, 120
(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. A049317, A049319.
Sequence in context: A023842 A061795 A110261 this_sequence A079551 A008805 A026925
Adjacent sequences: A049315 A049316 A049317 this_sequence A049319 A049320 A049321
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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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