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 A280649 #8 Dec 23 2024 14:53:45
%S A280649 28,33,41,108,132,157,159,175,178,181,184,187,190,193,196,204,207,209,
%T A280649 466,474,480,486,492,508,514,515,518,519,528,536,539,552,570,588,611,
%U A280649 627,638,648,651,657,658,659,660,706,707,708,714,719,745,757,763,765,772
%N A280649 Numbers k such that k^3 has an odd number of digits and the middle digit is 9.
%C A280649 The sequence of cubes starts: 21952, 35937, 68921, 1259712, 2299968, 3869893, 4019679, 5359375, ...
%H A280649 Lars Blomberg, <a href="/A280649/b280649.txt">Table of n, a(n) for n = 1..10000</a>
%H A280649 Jeremy Gardiner, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2016-December/017135.html">Middle digit in cube numbers</a>, Seqfan Mailing list, Dec 12 2016.
%e A280649 28^3 = 21(9)52, 181^3 = 592(9)741, 536^3 = 1539(9)0656.
%t A280649 ond9Q[n_]:=Module[{idn=IntegerDigits[n^3],len},len=Length[idn];OddQ[len]&&idn[[(len+1)/2]]==9]; Select[Range[800],ond9Q] (* _Harvey P. Dale_, Mar 14 2018 *)
%Y A280649 Cf. A280640-A280648, A181354.
%Y A280649 See A279420-A279429 for a k^2 version.
%Y A280649 See A279430-A279431 for a k^2 version in base 2.
%K A280649 nonn,base,easy
%O A280649 1,1
%A A280649 _Lars Blomberg_, Jan 07 2017