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%I #35 Aug 26 2014 01:46:42
%S 1,10,3240,3321,13041,13203,15400,65341,80200,90100,161028,210276,
%T 260281,265356,266085,300700,346528,500500,937765,947376,1043290,
%U 1228528,1313010,1628110,2049300,2390391,2421100,3357936,3746953,4020030,5250420,6641190,6857956,6939675
%N Triangular numbers divisible by the square of the sum of their digits.
%C Intersection of A000217 and A072081.
%H K. D. Bajpai, <a href="/A243008/b243008.txt">Table of n, a(n) for n = 1..12445</a>
%e a(3) = 3240 = 80 * (80 + 1)/2 is a triangular number. Since 3240 is divisible by (3 + 2 + 4 + 0)^2 = 81, it appears in the sequence.
%e a(3) = 3321 = 81 * (81 + 1)/2 is a triangular number. Since 3321 is divisible by (3 + 3 + 2 + 1)^2 = 81, it appears in the sequence.
%t Select[Table[n*(n + 1)/2, {n, 10000}], Divisible[#, Plus @@ IntegerDigits[#]^2] &]
%o (PARI)
%o for(n=1,10^4,s=n*(n+1)/2;if(s%(sumdigits(s)^2)==0,print1(s,", "))) \\ _Derek Orr_, Aug 23 2014
%Y Cf. A000217, A072081, A076713, A118693.
%K nonn,base
%O 1,2
%A _K. D. Bajpai_, Aug 20 2014
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