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 A270542 #38 Apr 07 2016 02:53:32
%S A270542 0,1,2704,5184,7744
%N A270542 Numbers of the form (pq)^2, where p is the number of digits of n (A055642) and q is the sum of the digits of n (A007953).
%e A270542 2704 is a term because 2704 = [4*(2+7+0+4)]^2;
%e A270542 5184 is a term because 5184 = [4*(5+1+8+4)]^2.
%t A270542 Position[ Table[ IntegerLength[k] Sum[( Floor[k/10^n] - 10 Floor[k/10^(n + 1)]), {n, 0, IntegerLength@ k^2}] - k, {k, 1, 10^6}], 0] // Flatten = {1, 1232, 4100, 268542}
%t A270542 Select[Range[10^3]^2,With[{id=IntegerDigits[#]},#==(Length[id]*Plus@@id)^2]&] (* _Ray Chandler_, Apr 01 2016 *)
%o A270542 (PARI) isok(n) = d = digits(n); (#d*vecsum(d))^2 == n; \\ _Michel Marcus_, Mar 26 2016
%Y A270542 Cf. A007953, A055642, A257784.
%K A270542 nonn,base,fini,full
%O A270542 1,3
%A A270542 _José de Jesús Camacho Medina_, Mar 18 2016