OFFSET
1,2
COMMENTS
1 and 3 are the only terms with less than two prime factors.
LINKS
Klaus Brockhaus, Table of n, a(n) for n=1..1000
EXAMPLE
a(6) = 3 * 7, a(7) = 2^2 * 7, a(8) = 2^2 * 3^2.
MATHEMATICA
Select[Accumulate[Range[0, 320]] , PrimeNu[#]<3&] (* James C. McMahon, Sep 17 2024 *)
PROG
(PARI) for(n=1, 320, k=binomial(n+1, 2); if(omega(k)<=2, print1(k, ", "))) \\ Klaus Brockhaus, Jul 30 2006
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Greg Huber, Jul 28 2006
EXTENSIONS
More terms from Klaus Brockhaus, Jul 30 2006 and May 21 2008
STATUS
approved