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 A260144 #24 May 26 2025 18:27:33
%S A260144 1568,14049280,140492800,368089904,506300928,1404928000,14049280000,
%T A260144 124856008704,140492800000,1404928000000
%N A260144 Numbers k such that there exist two numbers a and b where k = a.b = sigma(a)*phi(b) ("." means concatenation).
%C A260144 The sequence is infinite because, for m>0, 14049280*10^m = sigma(1404) * phi(9280*10^m).
%e A260144 1568 is in the sequence because 1568 = sigma(156) * phi(8).
%Y A260144 Cf. A000010, A000203, A159000, A253824.
%K A260144 nonn,base,more
%O A260144 1,1
%A A260144 _Paolo P. Lava_ and _Giovanni Resta_, Jul 17 2015
%E A260144 a(7)-a(10) from _Max Alekseyev_, May 26 2025