A049319 Number of 3-dimensional integer direction vectors (a,b,c) towards grid points at squared integer distance 2n-1.

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.

Links

Table of n, a(n) for n=1..52.

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

Cf. A049318, A049317.

Sequence in context: A298038 A223751 A228745 * A203984 A237836 A231324

Adjacent sequences: A049316 A049317 A049318 * A049320 A049321 A049322

Keyword

nonn

Author

Wouter Meeussen

Extensions

Missing a(40)=480 inserted by Sean A. Irvine, Jul 28 2021

Status

approved