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%I #3 Jun 21 2013 16:46:44
%S 0,1,8,38,165,1020,5360,24553,98442
%N Number of n-digit numbers x such that the digits of x^2 occur with frequency 2.
%C After a(10), all terms are 0.
%e The only two-digit number is 88, whose square is 7744.
%t 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 Cf. A225428.
%K nonn,base
%O 1,3
%A _T. D. Noe_, Jun 21 2013
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