|
%I #19 Apr 11 2020 04:55:40
%S -1,2,3,5,6,8,9,11,12,14,15,17,18,20,21,23,24,26,27,29,30,32,33,35,36,
%T 38,39,41,42,44,45,47,48,50,51,53,54,56,57,59,60,62,63,65,66,68,69,71,
%U 72,74,75,77,78,80,81,83,84,86,87,89,90,92,93,95,96,98,99,101,102,104
%N Inscribe 2 spheres of curvature 2 inside sphere of curvature -1, continue to inscribe spheres where possible; sequence gives list of curvatures.
%C A 3-dimensional Apollonian (or Soddy) problem.
%C Appears to be congruent to 0 or 2 mod 3.
%F Appears to coincide with a(n)=2+3*floor((n-1)/2)+(1+(-1)^n)/2-0^n, in which case the g.f. is (-1+3x+2x^2-x^3)/((1+x)(1-x)^2). - _Paul Barry_, Sep 11 2008
%Y Cf. A042944.
%K sign,nice
%O 0,2
%A _Brian Galebach_
|
