A279427 Numbers k such that k^2 has an odd number of digits and the middle digit is 7.

24, 26, 113, 137, 144, 154, 181, 189, 214, 223, 234, 266, 277, 286, 311, 1033, 1038, 1043, 1057, 1062, 1071, 1076, 1085, 1099, 1108, 1117, 1126, 1139, 1148, 1152, 1161, 1165, 1178, 1182, 1199, 1203, 1228, 1232, 1236, 1240, 1244, 1248, 1252, 1256, 1260, 1264

Offset

1,1

Links

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

Example

24^2 = 5(7)6, 223^2 = 49(7)29, 1152^2 = 132(7)104.

Mathematica

Select[Range[1264], OddQ[len=Length[IntegerDigits[#^2]]]&&Part[IntegerDigits[#^2], (len+1)/2]==7 &] (* Stefano Spezia, Oct 03 2023 *)

Crossrefs

Cf. A279420-A279426, A279428-A279429.

Sequence in context: A336237 A058627 A286130 * A116203 A345499 A071833

Adjacent sequences: A279424 A279425 A279426 * A279428 A279429 A279430

Keyword

nonn,base,easy

Author

Lars Blomberg, Dec 22 2016

Status

approved