OFFSET
1,1
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
EXAMPLE
15 has three proper divisors {1,3,5} and so is on the list; 16 has four {1,2,4,8} and so is not; 17 has one {1} and so is not; 18 has five {1,2,3,6,9} and so is.
PROG
(PARI) n=0; for (m=1, 10^9, if(isprime(numdiv(m) - 1), write("b063806.txt", n++, " ", m); if (n==1000, break))) \\ Harry J. Smith, Aug 31 2009
(PARI) is(n)=isprime(numdiv(n)-1) \\ Charles R Greathouse IV, Sep 18 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Aug 20 2001
STATUS
approved