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 A280644 #8 Dec 23 2024 14:53:45 %S A280644 7,104,112,140,143,158,166,186,188,195,465,467,490,541,558,572,595, %T A280644 598,604,605,606,607,613,616,622,625,630,634,635,640,643,647,653,667, %U A280644 675,679,687,702,712,718,720,727,734,738,759,764,783,787,802,810,815,818 %N A280644 Numbers k such that k^3 has an odd number of digits and the middle digit is 4. %C A280644 The sequence of cubes starts: 343, 1124864, 1404928, 2744000, 2924207, 3944312, 4574296, 6434856, ... %H A280644 Lars Blomberg, <a href="/A280644/b280644.txt">Table of n, a(n) for n = 1..10000</a> %H A280644 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 A280644 7^3 = 3(4)3, 195^3 = 741(4)875, 640^3 = 2621(4)4000 %t A280644 Select[Range[1000],OddQ[IntegerLength[#^3]]&&NumberDigit[#^3,(IntegerLength[ #^3]-1)/2]==4&] (* _Harvey P. Dale_, Aug 12 2021 *) %Y A280644 Cf. A280640-A280643, A280645-A280649, A181354. %Y A280644 See A279420-A279429 for a k^2 version. %Y A280644 See A279430-A279431 for a k^2 version in base 2. %K A280644 nonn,base,easy %O A280644 1,1 %A A280644 _Lars Blomberg_, Jan 07 2017