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 A325278 #7 Apr 17 2019 19:09:05
%S A325278 1,2,4,6,12,60,2520,1286485200,35933692027611398678865941374040400000
%N A325278 Smallest number with adjusted frequency depth n.
%C A325278 The adjusted frequency depth of a positive integer n is 0 if n = 1, and otherwise it is 1 plus the number of times one must apply A181819 to reach a prime number, where A181819(k = p^i*...*q^j) = prime(i)*...*prime(j) = product of primes indexed by the prime exponents of k. For example, 180 has adjusted frequency depth 5 because we have: 180 -> 18 -> 6 -> 4 -> 3.
%C A325278 Differs from A182857 in having 2 instead of 3.
%t A325278 nn=10000;
%t A325278 fd[n_]:=Switch[n,1,0,_?PrimeQ,1,_,1+fd[Times@@Prime/@Last/@FactorInteger[n]]];
%t A325278 fds=fd/@Range[nn];
%t A325278 Sort[Table[Position[fds,x][[1,1]],{x,Union[fds]}]]
%Y A325278 A subsequence of A325238.
%Y A325278 Cf. A011784, A056239, A112798, A118914, A181819, A181821, A182857, A225485, A323023, A325258, A325272, A325277, A325278, A325280.
%Y A325278 Omega-sequence statistics: A001222 (first omega), A001221 (second omega), A071625 (third omega), A323022 (fourth omega), A304465 (second-to-last omega), A182850 or A323014 (length/frequency depth), A325248 (Heinz number).
%K A325278 nonn
%O A325278 0,2
%A A325278 _Gus Wiseman_, Apr 17 2019