A279423 - OEIS

A279423

Numbers k such that k^2 has an odd number of digits and the middle digit is 3.

111, 124, 128, 139, 146, 156, 177, 188, 213, 231, 269, 287, 312, 1036, 1041, 1055, 1060, 1074, 1088, 1097, 1106, 1115, 1124, 1133, 1146, 1159, 1172, 1189, 1193, 1214, 1218, 1222, 1226, 1274, 1278, 1282, 1286, 1305, 1309, 1313, 1328, 1343, 1354, 1365, 1376

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OFFSET

1,1

LINKS

Lars Blomberg, Table of n, a(n) for n = 1..10000

EXAMPLE

111^2 = 12(3)21, 231^2 = 53(3)61, 1214^2 = 147(3)796.

MATHEMATICA

ond3Q[n_]:=Module[{idn2=IntegerDigits[n^2], len}, len=Length[idn2]; OddQ[ len] && idn2[[(len+1)/2]]==3]; Select[Range[1400], ond3Q] (* Harvey P. Dale, Apr 06 2018 *)

CROSSREFS

Cf. A279420-A279422, A279424-A279429.

Sequence in context: A135643 A070798 A235039 * A213879 A095613 A108721

Adjacent sequences: A279420 A279421 A279422 * A279424 A279425 A279426

KEYWORD

nonn,base,easy

AUTHOR

Lars Blomberg, Dec 22 2016

STATUS

approved