Update: To generate a list of spheres similar to the circles in OP (sphere k just touching sphere k-2):
ClearAll[tr]
tr[n_] := (2 n^2 - 1 + (-1)^n)/4;
Graphics[Translate[Scale[Circle[], #], {tr @ #, 0}] & /@ Range[10]]
Graphics3D[{Opacity[.5], Translate[Scale[Sphere[], #], {tr@#, 0, 0}] & /@ Range[10]},
Boxed -> False]
Original answer:
You can use Translate and Scale Sphere[] as follows:
radii = Range[5];
Graphics3D[Translate[Scale[Sphere[], #], {#^2, 0, 0}] & /@ radii]
or translate to leave gaps between spheres:
translations = 2 Accumulate[radii];
Graphics3D[MapThread[Translate[Scale[Sphere[], #], {#2, 0, 0}] &, {radii, translations}]]
