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 A240529 #27 Sep 08 2022 08:46:07
%S A240529 224,351,624,704,735,768,783,800,832,864,895,944,959,960,999,1151,
%T A240529 1152,1224,1279,1343,1344,1375,1440,1520,1539,1824,1855,1935,1943,
%U A240529 1944,1952,2000,2144,2159,2176,2187,2295,2367,2430,2432,2464,2495,2496,2499,2511
%N A240529 Indices of 9-almost prime triangular numbers.
%H A240529 Vincenzo Librandi, <a href="/A240529/b240529.txt">Table of n, a(n) for n = 1..1000</a>
%F A240529 { m : A069904(m) = 9 }. - _Alois P. Heinz_, Aug 05 2019
%e A240529 a(1) = 224 because A000217(224) = 224*(224+1)/2 = 25200 = 2^4 * 3^2 * 5^2 * 7 is a 9-almost prime.
%t A240529 Flatten[Position[Accumulate[Range[3500]], _?(PrimeOmega[#]== 9 &)]]
%t A240529 Select[Range[3000], PrimeOmega[(# (# + 1))/2] == 9 &] (* _Harvey P. Dale_, Jun 22 2017 *)
%o A240529 (Magma) [n: n in [2..2600] | &+[d[2]: d in Factorization((n*(n+1)))] eq 10]; // _Vincenzo Librandi_, Dec 22 2018
%o A240529 (GAP) F:=List([1..2600],n->Length(Factors(n*(n+1)/2)));; a:=Filtered([1..Length(F)],i->F[i]=9); # _Muniru A Asiru_, Dec 22 2018
%Y A240529 Cf. A000217, A069904, A108815, A114435, A114436, A114437, A164977.
%K A240529 nonn,easy
%O A240529 1,1
%A A240529 _Vincenzo Librandi_, Apr 07 2014