OFFSET
1,1
COMMENTS
Terms are 2^2, 2^3, 3*2^3, 3^3, 2^5, 3*2^5, 3^7, 2^13, 3*2^13, ...
EXAMPLE
4 is a term because uphi(4) = 3 does not divide uphi(4!) = 14.
PROG
(PARI) valp(n, p)=my(s); while(n\=p, s+=n); s
uphi(n, f=factor(n))=prod(i=1, #f~, f[i, 1]^f[i, 2]-1)
is(n)=my(m=uphi(n), t); forprime(p=2, n, t=gcd(lift(Mod(p, m)^valp(n, p)-1), m); if(t>1, m/=t; if(m==1, return(0)))); m>1 \\ Charles R Greathouse IV, Aug 27 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Aug 26 2017
EXTENSIONS
a(10)-a(19) from Charles R Greathouse IV, Aug 27 2017
a(20) from Charles R Greathouse IV, Sep 06 2017
a(21) from Charles R Greathouse IV, Oct 12 2017
a(22)-a(27) from Max Alekseyev, Jan 28 2024
STATUS
approved