OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
20*21/2 = 2*3*5*7 = 210 is the smalles triangular number with more than three distinct prime factors, hence a(1) = 210.
MATHEMATICA
Select[Accumulate[Range[200]], PrimeNu[#]>3&] (* Harvey P. Dale, Jun 06 2013 *)
PROG
(PARI) for(n=1, 100, k=binomial(n+1, 2); if(omega(k)>3, print1(k, ", ")))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Klaus Brockhaus, Aug 01 2006
STATUS
approved