OFFSET
1,1
MATHEMATICA
Select[Range[2000], EulerPhi[#]/CarmichaelLambda[#] == 12 &] (* Alonso del Arte, Apr 17 2017 *)
PROG
(PARI) {cmf(f)=if( ((f[1]==2)&&(f[2]>2)), eulerphi(f[1]^f[2])/2, eulerphi(f[1]^f[2])) }
{cl(f)= k=factor(f); l=1; for(x=1, omega(f), l=lcm(l, cmf([k[x, 1], k[x, 2]]))); l }
{A0(n)=eulerphi(n)/cl(n)}
for(x=1, 10001, if(A0(x)==12, print1(x, ", ")))
(PARI) isok(k) = eulerphi(k)/lcm(znstar(k)[2]) == 12; \\ Michel Marcus, May 25 2022
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Randall L Rathbun, Jan 12 2002
STATUS
approved