%I A116544
%S A116544 0,1,3,6,10,28,45,55,78,105,120,190,210,231,253,276,300,325,378,406,435,
%T A116544 465,528,561,595,630,703,741,780,820,861,903,990,1035,1081,1128,1225,
%U A116544 1275,1378,1485,1540,1596,1653,1770,1830,2016,2080,2145,2278,2346,2415
%N A116544 Triangular numbers for which the multiplicative digital root is also 
               a triangular number.
%t A116544 a = {}; For[n = 0, n < 100, n++, b = n*(n + 1)/2; While[b > 9, b = Times 
               @@ IntegerDigits[b]]; If[Length[Intersection[{b}, {0, 1, 3, 6}]] 
               == 1, AppendTo[a, n*(n + 1)/2]]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), 
               Jan 02 2008
%Y A116544 Sequence in context: A048006 A068818 A137173 this_sequence A068866 A110891 
               A115887
%Y A116544 Adjacent sequences: A116541 A116542 A116543 this_sequence A116545 A116546 
               A116547
%K A116544 nonn,base
%O A116544 1,3
%A A116544 Luc Stevens (lms022(AT)yahoo.com), Apr 03 2006
%E A116544 More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), 
               Jan 02 2008