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 A331393 #14 Feb 25 2021 02:18:59 %S A331393 0,2,6,16,36,82,176,372,768,1582,3224,6534,13166,26504,53244,106824, %T A331393 214060,428764,858400,1718056,3437734,6877896,13759154,27523128, %U A331393 55052582,110114618,220242288,440503282,881031714,1762100362,3524251618,7048576724,14097253490 %N A331393 Sum, over all binary strings w of length n, of the length of the longest border of w. %C A331393 A nonempty word w is a border of a string x if w is both a prefix and suffix of x, and w does not equal x. %H A331393 Shiyao Guo, <a href="/A331393/b331393.txt">Table of n, a(n) for n = 1..120</a> %e A331393 For n = 4 the 16 words are 0000,0001,0010,0011,0100,0101,0110,0111, and their binary complements. %e A331393 0000 has longest border 3; 0010, 0100, 0110 have longest border 1; and 0101 has longest border 2. So a(4) = 2*(3+3+2) = 16. %Y A331393 Cf. A094536, A331392. %K A331393 nonn %O A331393 1,2 %A A331393 _Jeffrey Shallit_, Jan 15 2020 %E A331393 More terms from _Rémy Sigrist_, Jan 16 2020