This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A121479 #6 Jun 06 2013 11:49:31 %S A121479 210,630,780,990,1326,1540,1596,1770,1830,2145,2346,2415,2850,2926, %T A121479 3003,3486,3570,3828,4095,4186,4278,4560,4950,5460,5565,6105,6216, %U A121479 6555,6670,6786,7140,7260,7626,8385,8646,8778,9180,9730,9870,10296,10440,10878 %N A121479 Triangular numbers with more than three distinct prime factors. %H A121479 Harvey P. Dale, <a href="/A121479/b121479.txt">Table of n, a(n) for n = 1..1000</a> %e A121479 20*21/2 = 2*3*5*7 = 210 is the smalles triangular number with more than three distinct prime factors, hence a(1) = 210. %t A121479 Select[Accumulate[Range[200]],PrimeNu[#]>3&] (* _Harvey P. Dale_, Jun 06 2013 *) %o A121479 (PARI) for(n=1,100,k=binomial(n+1,2);if(omega(k)>3,print1(k,","))) %Y A121479 Cf. A000217, A068443, A119663, A121478. %K A121479 easy,nonn %O A121479 1,1 %A A121479 _Klaus Brockhaus_, Aug 01 2006