%I #24 Apr 21 2021 11:19:49
%S 759576,97759786,97957576,887579686,987759576,987859786,7599859786,
%T 7679576587,8756697886,8766958976,9775989867,9897756766,9978965766,
%U 76797588887,88766997576,97978858887,99777685676,99789658666,99879856766,767897685676,869866586666
%N Numbers k such that the decimal expansions of both k and k^2 have 5 as the digit with the smallest value and 9 as the digit with the largest value.
%C The first digit of a term is either 7, 8 or 9 and the last digit is either 5, 6 or 7. Conjecture: no term is a multiple of 5. - _Chai Wah Wu_, Sep 10 2017
%H Chai Wah Wu, <a href="/A254074/b254074.txt">Table of n, a(n) for n = 1..1224</a> (n = 1..326 from Hiroaki Yamanouchi).
%t fQ[n_] := Block[{c = DigitCount@ n}, And[Plus @@ Take[c, {1, 4}] == 0, Last@ c == 0, c[[5]] > 0, c[[9]] > 0]]; Select[Range@ 10000000, fQ@ # && fQ[#^2] &] (* _Michael De Vlieger_, May 05 2015 *)
%o (PARI) is(n) = vecmin(digits(n))==5 && vecmin(digits(n^2))==5 && vecmax(digits(n))==9 && vecmax(digits(n^2))==9
%Y Cf. A137147, A256630, A256631, A256633, A256634, A256708, A256709, A256889, A257197, A257210, A257211, A256601, A257310, A249915, A257123, A257368, A257485, A257486, A257498, A238553, A257534, A254071.
%K nonn,base
%O 1,1
%A _Felix Fröhlich_, May 03 2015
%E a(14)-a(21) from _Hiroaki Yamanouchi_, May 07 2015