OFFSET
1,1
COMMENTS
Comment: Most terms of this sequence have four divisors. Some terms (the squares of primes) have three divisors; very few terms have more than four divisors (the first such term is 4753, with six). Conjecture: This sequence is infinite. - Adam M. Kalman (mocha(AT)clarityconnect.com), Nov 11 2004
LINKS
Charles R. Greathouse IV, Sep 10, 2008, Table of n, a(n) for n = 1..10001
EXAMPLE
133 is a term, the divisors are 1,7,19,133 and no sum of two or more gives a prime.
MATHEMATICA
For[a:=4, a<=2000, s =Divisors[a]; n := 1; d := False; While[(n<=2^Length[s])\[And]( ["not" character]d), If[Length[NthSubset[n, s]]>=2, If[ !PrimeQ[Plus@@NthSubset[n, s]], n++, d:= True], n++ ]]; If[ ["not" character]d, Print[a]]; a++; While[PrimeQ[a], a+=2]]; (* Adam M. Kalman, Nov 11 2004 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Apr 23 2004
EXTENSIONS
Corrected and extended by Adam M. Kalman (mocha(AT)clarityconnect.com), Nov 11 2004
STATUS
approved