%I
%S 1,1,2,2,4,2,2,2,2,4,6,2,4,2,4,2,4,6,6,2,4,2,4,2,6,4,6,2,6,4,2,4,2,4,
%T 14,4,6,2,10,2,6,6,4,6,6,2,10,2,4,2,12,12,4,2,4,6,2,10,4,2,6,6,2,6,4,
%U 2,10,14,4,2,4,14,6,10,2,4,6,8,6,4,2,4,6,8,4,8,10,2,10,2,6,4,6,8,4,2,4,12,8
%N First differences of A097605 (phi(n) divides n^2  1).
%H G. C. Greubel, <a href="/A097884/b097884.txt">Table of n, a(n) for n = 1..1000</a>
%t A097605:= Select[Range[500], Mod[#^2  1, EulerPhi[#]] == 0 &]
%t Table[A097605[[n]]  A097605[[n  1]], {n, 2, 50}] (* _G. C. Greubel_, Dec 21 2017 *)
%Y Cf. A097605.
%K nonn
%O 1,3
%A _John W. Layman_, Sep 02 2004
