Let ABC be a triangle, A1B1C1 the circumcevian triangle of H and A2B2C2 the cevian triangle of G (medial triangle).
A3 = the other than A1 intersection of A1A2 and the circumcircle.
B3 = the other than B1 intersection of B1B2 and the circumcircle.
C3 = the other than C1 intersection of C1C2 and the circumcircle.
N1 = The NPC center of A3BC
N2 = The NPC center of B3CA
N3 = The NPC center of C3AB.
The four NPC centers N, N1,N2,N3 are concyclic (??).
Center of the circle?
APH, 14 February 2012