A281856 - OEIS

%I #8 Feb 03 2017 09:23:15

%S 1,1,2,2,2,3,2,3,2,4,5,6,3,6,4,3,5,6,4,8,6,10,6,9,4,9,8,12,5,8,11,6,6,

%T 10,9,15,6,8,6,16,14,10,6,18,11,15,18,8,15,10,8,12,12,9,10,18,12,9,22,

%U 14,18,24,8,20

%N One fourth of the order of the abelian non-cyclic groups (Z/A033949(n)*Z)^x.

%C a(n) is one fourth of the row product of the irregular triangle A281854.

%F a(n) = A000010(A033949(n))/4, n >= 1.

%t EulerPhi@ Select[Range[2, 130], ! IntegerQ@ PrimitiveRoot@ # &]/4 (* _Michael De Vlieger_, Feb 02 2017 *)

%Y Cf. A000010, A033949, A060679, A281854.

%K nonn

%O 1,3

%A _Wolfdieter Lang_, Feb 02 2017