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 A225429 #3 Jun 21 2013 16:46:44
%S A225429 0,1,8,38,165,1020,5360,24553,98442
%N A225429 Number of n-digit numbers x such that the digits of x^2 occur with frequency 2.
%C A225429 After a(10), all terms are 0.
%e A225429 The only two-digit number is 88, whose square is 7744.
%t A225429 cnt = 0; t2 = Table[x = Floor[Sqrt[10] * 10^(n-1)]; While[x < 10^n, If[Union[Last[Transpose[Tally[IntegerDigits[x^2]]]]] == {2}, cnt++]; x++]; cnt, {n, 6}]; Join[{0}, Differences[t2]]
%Y A225429 Cf. A225428.
%K A225429 nonn,base
%O A225429 1,3
%A A225429 _T. D. Noe_, Jun 21 2013