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A049319
Number of 3-dimensional integer direction vectors (a,b,c) towards grid points at squared integer distance 2n-1.
2
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, 480, 648, 504, 384, 672, 528, 576, 768, 480, 576, 864, 600, 624
OFFSET
1,1
COMMENTS
A vector is a direction vector if its nonzero components have their GCD = 1.
EXAMPLE
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 ]
CROSSREFS
Sequence in context: A298038 A223751 A228745 * A203984 A237836 A231324
KEYWORD
nonn
EXTENSIONS
Missing a(40)=480 inserted by Sean A. Irvine, Jul 28 2021
STATUS
approved