This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A074315 #18 Mar 01 2025 03:19:33
%S A074315 36,66,78,120,210,276,300,378,528,630,666,780,820,990,1128,1176,1326,
%T A074315 1540,1596,1770,1830,2016,2080,2346,2556,2628,2850,3160,3240,3486,
%U A074315 3570,3828,4095,4278,4560,4656,4950,5460,5778,5886,6216,6328,6786,7140,7260
%N A074315 Abundant triangular numbers.
%H A074315 Amiram Eldar, <a href="/A074315/b074315.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)
%F A074315 Intersection of A000217 and A005101. - _Michel Marcus_, Mar 10 2013
%e A074315 a(2) = 66 because the sum of aliquot divisors of 66 (which is a triangular number) is 1+2+3+6+11+22+33 = 78 which is greater than 66, hence it is abundant. 66 is the 2nd abundant triangular number.
%t A074315 Select[Accumulate[Range[150]],Total[Divisors[#]]>2#&] (* _Harvey P. Dale_, Dec 18 2014 *)
%o A074315 (PARI) listA074315(m) = {for (i=1, m, t = i*(i+1)/2; if (sigma(t) > 2*t, print1(t, ", ")););} \\ up to the m-th triangular number; _Michel Marcus_, Mar 10 2013
%Y A074315 Cf. A000217, A005101.
%K A074315 nonn
%O A074315 1,1
%A A074315 _Shyam Sunder Gupta_, Sep 22 2002