This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A279429 #7 Oct 03 2023 18:44:52 %S A279429 3,14,114,118,130,134,148,158,161,170,173,176,187,212,219,228,230,270, %T A279429 272,281,288,313,1034,1039,1044,1058,1063,1072,1077,1086,1095,1109, %U A279429 1118,1131,1140,1153,1166,1183,1204,1208,1292,1296,1315,1319,1334,1345,1349 %N A279429 Numbers k such that k^2 has an odd number of digits and the middle digit is 9. %H A279429 Lars Blomberg, <a href="/A279429/b279429.txt">Table of n, a(n) for n = 1..10000</a> %e A279429 3^2 = (9), 170^2 = 28(9)00, 1086^2 = 117(9)396. %t A279429 Select[Range[1349], OddQ[len=Length[IntegerDigits[#^2]]]&&Part[IntegerDigits[#^2], (len+1)/2]==9 &] (* _Stefano Spezia_, Oct 03 2023 *) %Y A279429 Cf. A279420-A279428. %K A279429 nonn,base,easy %O A279429 1,1 %A A279429 _Lars Blomberg_, Dec 22 2016