0,2

A 3-dimensional Apollonian (or Soddy) problem.

Appears to be congruent to 0 or 2 mod 3.

Table of n, a(n) for n=0..69.

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

Cf. A042944.

Sequence in context: A248758 A267528 A294732 * A007494 A258575 A052490

Adjacent sequences: A045503 A045504 A045505 * A045507 A045508 A045509

sign,nice

Brian Galebach

approved