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A256708
Numbers n such that the decimal expansions of both n and n^2 have 0 as smallest digit and 8 as largest digit.
23
280, 508, 780, 805, 1028, 1078, 1280, 1308, 1680, 1780, 1805, 1840, 2078, 2608, 2680, 2780, 2800, 2801, 2802, 2805, 2840, 2850, 3280, 3580, 3780, 3805, 3808, 3850, 4048, 4078, 4280, 4780, 4804, 4805, 4880, 5008, 5018, 5028, 5048, 5078, 5080, 5084, 5180, 5280
OFFSET
1,1
LINKS
MATHEMATICA
fQ[n_] := Block[{c = DigitCount@ n}, And[c[[9]] == 0, c[[8]] > 0, c[[10]] > 0]]; Select[Range@ 5280, fQ@ # && fQ[#^2] &] (* Michael De Vlieger, Apr 12 2015 *)
maxdQ[n_]:=Module[{id1=IntegerDigits[n], id2=IntegerDigits[n^2]}, Max[ id1] == Max[ id2] == 8&&Min[id1]==Min[id2]==0]; Select[Range[6000], maxdQ] (* Harvey P. Dale, Oct 19 2021 *)
PROG
(PARI) is(n) = vecmin(digits(n))==0 && vecmin(digits(n^2))==0 && vecmax(digits(n))==8 && vecmax(digits(n^2))==8
KEYWORD
nonn,base
AUTHOR
Felix Fröhlich, Apr 08 2015
STATUS
approved