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%I #26 Aug 18 2021 07:57:53
%S 1,4,12,18,24,32,56,91,78,72,144,168,112,192,360,270,234,260,360,576,
%T 384,288,672,868,434,560,960,720,720,768,992,1488,864,864,1872,1482,
%U 760,1120,2352,1764,1344,1408,1584,2808,1872,1152,2880,3420,1767,2232
%N Sum of the divisors of n-th triangular number.
%C By definition a(n) is also the sum of the divisors of n-th generalized hexagonal number. - _Omar E. Pol_, Nov 24 2015
%H T. D. Noe, <a href="/A074285/b074285.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A000203(A000217(n)). - _Omar E. Pol_, Nov 24 2015
%F Sum_{k=1..n} a(k) ~ n^3/3. - _Vaclav Kotesovec_, Aug 18 2021
%e a(4)=18 because the sum of divisors of the 4th triangular number (i.e., 10) is 1 + 2 + 5 + 10 = 18.
%t Table[DivisorSigma[1, n*(n + 1)/2], {n, 1, 100}] (* _Vaclav Kotesovec_, Aug 18 2021 *)
%o (PARI) a(n) = sigma(n*(n+1)/2); \\ _Altug Alkan_, Nov 24 2015
%Y Cf. A000203, A000217, A330322.
%K nonn
%O 1,2
%A _Shyam Sunder Gupta_, Sep 21 2002
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