A257211 Numbers n such that the decimal expansions of both n and n^2 have 1 as smallest digit and 8 as largest digit.

128, 178, 871, 1128, 1178, 1218, 1258, 1278, 1284, 1328, 1358, 1368, 1478, 1678, 1681, 1768, 1778, 1784, 1785, 1828, 1874, 1881, 2681, 2861, 2871, 3418, 3581, 3718, 3816, 3841, 4178, 4318, 4815, 4831, 4841, 4881, 5178, 5181, 5182, 5318, 5815, 5841, 5871, 5881

Offset

1,1

Links

Felix Fröhlich, Table of n, a(n) for n = 1..10000

Mathematica

fQ[n_] := Block[{d = DigitCount@ n}, Plus @@ Take[d, {9, 10}] == 0 && d[[1]] > 0 && d[[8]] > 0]; Select[Range@ 6000, fQ@ # && fQ[#^2] &] (* Michael De Vlieger, Apr 20 2015 *)
sd1ld8Q[n_]:=With[{idn=IntegerDigits[n]}, Max[idn]==8&&Min[idn]==1]; Select[ Range[ 6000], AllTrue[{#, #^2}, sd1ld8Q]&] (* Harvey P. Dale, Oct 14 2022 *)

Prog

(PARI) is(n) = vecmin(digits(n))==1 && vecmin(digits(n^2))==1 && vecmax(digits(n))==8 && vecmax(digits(n^2))==8

Crossrefs

Cf. A256630, A256631, A256633, A256634, A256708, A256709, A256889, A257197, A257210, A256601.

Sequence in context: A114565 A243812 A194766 * A109651 A114408 A114418

Adjacent sequences: A257208 A257209 A257210 * A257212 A257213 A257214

Keyword

nonn,base

Author

Felix Fröhlich, Apr 18 2015

Status

approved