A279422 -id:A279422 - cp's OEIS frontend

A279421 Numbers k such that k^2 has an odd number of digits and the middle digit is 1.

1, 110, 119, 123, 127, 131, 142, 152, 182, 190, 210, 224, 237, 239, 261, 263, 276, 290, 310, 1035, 1040, 1059, 1073, 1087, 1096, 1105, 1123, 1132, 1141, 1145, 1154, 1167, 1171, 1184, 1188, 1209, 1213, 1217, 1285, 1289, 1293, 1312, 1316, 1331, 1346, 1357, 1368

Offset: 1

Lars Blomberg, Dec 22 2016

			1^2 = (1), 190^2 = 36(1)00, 1145^2 = 131(1)025.

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

Cf. A279420, A279422-A279429.

ond1Q[n_]:=Module[{len=IntegerLength[n^2]},OddQ[len]&&IntegerDigits[n^2][[(len+1)/2]]==1]; Select[Range[1500],ond1Q] (* Harvey P. Dale, Jun 06 2018 *)

A279423 Numbers k such that k^2 has an odd number of digits and the middle digit is 3.

Original entry on oeis.org

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

Offset: 1

Lars Blomberg, Dec 22 2016

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

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

Cf. A279420-A279422, A279424-A279429.

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 *)

cp's OEIS Frontend

A279421 Numbers k such that k^2 has an odd number of digits and the middle digit is 1.

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