OFFSET
1,1
PROG
(PARI) a(n) = forcomposite(c=1, , my(i=0); forcomposite(d=1, c-1, if(Mod(c, d)^(d-1)==1 && Mod(d, c)^(c-1)==1, i++)); if(i==n, return(c)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Mar 19 2016
STATUS
approved