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 A376704 #25 Oct 08 2024 18:38:33
%S A376704 16,24,36,40,54,56,60,81,84,90,100,126,135,140,150,189,196,210,225,
%T A376704 250,294,315,350,375,441,490,525,625,686,735,875,1029,1225,1715,2401,
%U A376704 14641,17303,20449,22627,24167,25289,26741,28561,29887,30613,31603,34969,35321,36179
%N A376704 4-brilliant numbers: numbers which are the product of four primes having the same number of decimal digits.
%H A376704 Paolo Xausa, <a href="/A376704/b376704.txt">Table of n, a(n) for n = 1..10000</a>
%H A376704 Dario Alpern, <a href="https://www.alpertron.com.ar/BRILLIANT4.HTM">4-Brilliant Numbers</a>.
%e A376704 35321 is a term because 35321 = 11 * 13 * 13 * 19, and these four prime factors have the same number of digits.
%t A376704 A376704Q[k_] := With[{f = FactorInteger[k]}, Total[f[[All, 2]]] == 4 && Length[Union[IntegerLength[f[[All, 1]]]]] == 1];
%t A376704 Select[Range[40000], A376704Q] (* or *)
%t A376704 dlist4[d_] := Sort[Times @@@ DeleteDuplicates[Map[Sort, Tuples[Prime[Range[PrimePi[10^(d-1)] + 1, PrimePi[10^d]]], 4]]]]; (* Generates terms with d-digits prime factors -- faster but memory intensive *)
%t A376704 Flatten[Array[dlist4, 2]]
%Y A376704 Subsequence of A014613.
%Y A376704 Cf. A078972, A376703, A376705, A376706.
%K A376704 nonn,base
%O A376704 1,1
%A A376704 _Paolo Xausa_, Oct 02 2024