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A112353 Triangular numbers that are the sum of three distinct positive triangular numbers. 2

%I #7 May 19 2019 02:14:24

%S 10,28,45,55,66,91,105,120,136,153,171,190,210,231,253,276,300,325,

%T 351,378,406,435,465,496,528,561,595,630,666,703,741,780,820,861,903,

%U 946,990,1035,1081,1128,1176,1225,1275,1326,1378,1431,1485

%N Triangular numbers that are the sum of three distinct positive triangular numbers.

%C Subsequence of A112355: it doesn't require the three positive triangular numbers to be distinct.

%e 45 is a term because 45 = 3 + 6 + 36 and these four numbers are distinct triangular numbers (A000217(9) = A000217(2) + A000217(3) + A000217(8)).

%t trnos=Accumulate[Range[200]];

%t Take[Union[Select[Total/@Subsets[trnos,{3}],MemberQ[trnos,#]&]],50] (* _Harvey P. Dale_, Jan 15 2011 *)

%Y Cf. A000217 (triangular numbers), A112352 (triangular numbers that are the sum of two distinct positive triangular numbers), A112355.

%K nonn

%O 1,1

%A _Rick L. Shepherd_, Sep 05 2005

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Last modified March 28 13:25 EDT 2024. Contains 371254 sequences. (Running on oeis4.)