2*uphi(x)=x, where the unitary phi function (A047994) is defined by if x=p1^r1*p2^r2*p3^r3*... then uphi(x)=(p1^r1-1)(p2^r2-1)(p3^r3-1)...
2, 12, 168, 240, 14880, 65280, 7608944640, 4294901760, 1125874137169920
2 seqfan posts
Sat Dec 20 06:02:46 CET 2008 [seqfan] UPhi(x)=UPhi(y)=1/8*(5*Sqroot(x)-3*Sqroot(y))^2