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 A076578 #19 Jan 13 2025 06:34:17
%S A076578 36,136,210,276,351,666,820,1035,1225,1275,1326,1431,1770,1830,1953,
%T A076578 2145,2346,2415,2775,2926,3003,3486,3916,4005,4186,4278,5050,5356,
%U A076578 5565,6105,6555,6670,6903,7626,8001,8385,8646,9316,9730,10731,11175,11325,11476,11935
%N A076578 Triangular numbers which are 4-almost primes.
%H A076578 Alois P. Heinz, <a href="/A076578/b076578.txt">Table of n, a(n) for n = 1..10000</a>
%e A076578 36 is a term because it is a triangular number and 36 = 2*2*3*3, i.e., is a product of 4 prime factors so is a 4-almost prime.
%p A076578 q:= n-> is(numtheory[bigomega](n)=4):
%p A076578 select(q, [i*(i+1)/2$i=0..200])[]; # _Alois P. Heinz_, Mar 27 2024
%t A076578 q[n_] := PrimeOmega[n] == 4;
%t A076578 Select[Table[i*(i+1)/2, {i, 0, 200}], q] (* _Jean-François Alcover_, Jan 13 2025, after _Alois P. Heinz_ *)
%Y A076578 Intersection of A000217 and A014613.
%Y A076578 Cf. A068443, A075875.
%K A076578 easy,nonn
%O A076578 1,1
%A A076578 _Shyam Sunder Gupta_, Oct 19 2002