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 A338572 #9 Feb 16 2025 08:34:00
%S A338572 0,1,2,0,3,4,5,0,1,6,7,2,8,9,10,0,11,3,12,4,13,14,15,1,5,16,2,6,17,18,
%T A338572 19,0,20,21,22,0,23,24,25,3,26,27,28,7,8,29,30,1,9,10,31,11,32,4,33,5,
%U A338572 34,35,36,12,37,38,13,0,39,40,41,14,42,43,44,0,45,46,15,16,47,48,49,2
%N A338572 Number of integers less than n with the same number of factorizations into prime powers as n.
%H A338572 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AbelianGroup.html">Abelian Group</a>
%F A338572 a(n) = |{j < n : A000688(j) = A000688(n)}|.
%e A338572 a(18) = 3 because A000688(18) = 2 and also A000688(4) = A000688(9) = A000688(12) = 2.
%t A338572 Table[Length[Select[Range[n - 1], FiniteAbelianGroupCount[#] == FiniteAbelianGroupCount[n] &]], {n, 80}]
%o A338572 (PARI) nf(n) = my(f=factor(n)[, 2]); prod(i=1, #f, numbpart(f[i])); \\ A000688
%o A338572 a(n) = my(nb=nf(n)); sum(k=1, n-1, nf(k) == nb); \\ _Michel Marcus_, Nov 03 2020
%Y A338572 Cf. A000688, A338568, A338569.
%K A338572 nonn
%O A338572 1,3
%A A338572 _Ilya Gutkovskiy_, Nov 03 2020