OFFSET
1,1
COMMENTS
The sequence contains all numbers of the form (Mersenne Prime)+1 as a subset. - Hugo Pfoertner, Sep 10 2004
EXAMPLE
a(19)=109051904=13*2^23: 24 prime factors, a(20)=169869312=3^4*2^21: 25 prime factors, a(21)=654311424=13*3*2^24: 26 prime factors. a(19)-1, a(20)-1 and a(21)-1 are primes.
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
G. L. Honaker, Jr., Jan 13 2002
EXTENSIONS
More terms from Jason Earls, Jan 15 2002
More terms from Hugo Pfoertner, Sep 10 2004
a(24)-a(27) from Donovan Johnson, Dec 08 2009
STATUS
approved