OFFSET
1,1
MATHEMATICA
Select[Range[8000], EulerPhi[#]/CarmichaelLambda[#]==18&] (* Harvey P. Dale, Jun 06 2018 *)
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)==18, print1(x, ", ")))
(PARI) isok(k) = eulerphi(k)/lcm(znstar(k)[2]) == 18; \\ Michel Marcus, May 25 2022
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Randall L Rathbun, Jan 12 2002
EXTENSIONS
Corrected by T. D. Noe, Nov 01 2006
STATUS
approved