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%I #10 Mar 02 2022 12:28:37
%S 36,153,2556,3240,4851,5778,9045,11628,13041,14535,17766,19503,33930,
%T 41328,46665,49455,52326,71253,74691,81810,85491,93096,109278,122265,
%U 131328,140715,145530,160461,170820,181503,186966,192510,203841,252405,258840,265356
%N Triangular numbers for which the sum of the digits equals the sum of the digits of the next triangular number.
%C s(n) stands for the sum of the digits of n. Each number of the sequence is divisible by 9.
%H Harvey P. Dale, <a href="/A117511/b117511.txt">Table of n, a(n) for n = 1..1000</a>
%F s(a(n))=s(a(n+1))
%e 153 is in the sequence because (1) 153 is triangular number a(18), triangular number a(19)=171 and (2) 1+5+3=1+7+1
%t Transpose[With[{c=Partition[Accumulate[Range[2000]],2,1]}, Select[c, Total[IntegerDigits[First[#]]]==Total[IntegerDigits[Last[#]]]&]]] [[1]] (* _Harvey P. Dale_, Oct 18 2011 *)
%t (#(#+1))/2&/@(SequencePosition[Total[IntegerDigits[#]]&/@Accumulate[ Range[ 1000]],{x_,x_}][[All,1]]) (* _Harvey P. Dale_, Mar 02 2022 *)
%Y Cf. A000217.
%K base,nonn
%O 1,1
%A Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
%E Corrected by Harvey P. Dale, Oct 18 2011
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