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%I #10 Jul 28 2021 22:51:08
%S 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,
%T 48,42,36,60,45,48,72,42,51,72,54,57,60,72,60,81,63,54,84,69,72,96,60,
%U 75,108,78,78,96,81,84,108,87,72,108,96,99,120,78,96,132,99,120
%N 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.
%C A vector is a direction vector if its nonzero components have their GCD = 1.
%e 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 ]
%Y Cf. A049317, A049319.
%K nonn
%O 1,1
%A _Wouter Meeussen_
%E Missing a(52)=78 inserted by _Sean A. Irvine_, Jul 28 2021
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