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 A056518 #9 Aug 22 2017 20:53:14 %S A056518 0,1,1,2,3,4,7,10,14,21,31,42,63,91,123,184,255,371,511,750,1015,1519, %T A056518 2047,3030,4092,6111,8176,12222,16383,24486,32767,49024,65503,98175, %U A056518 131061,196308,262143,392959,524223,785910,1048575,1572256,2097151,3144702,4194162 %N A056518 Number of primitive (period n) periodic palindromic structures using exactly two different symbols. %C A056518 For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure. %D A056518 M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2] %F A056518 A056513(n)-A000007(n-1). %Y A056518 Column 2 of A285037. %Y A056518 Cf. A056481. %K A056518 nonn %O A056518 1,4 %A A056518 _Marks R. Nester_ %E A056518 a(17)-a(45) from _Andrew Howroyd_, Apr 08 2017