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 A193803 #9 Jul 12 2017 11:57:03 %S A193803 3,6,9,12,15,18,22,29,36,43,46,50,57,64,68,71,79,90,101,108,112,123, %T A193803 134,138,145,153,156,168,175,183 %N A193803 Length of perfect Wichmann rulers. %C A193803 R is a perfect Wichmann ruler iff R is a perfect ruler (for definition see A103294) and there exist two integers r>=0 and s>=0 such that the type of the difference representation of the ruler is [1*r, r+1, (2r+1)*r, (4r+3)*s, (2r+2)*(r+1), 1*r]. %H A193803 L. Egidi and G. Manzini, <a href="http://www.di.unipmn.it/TechnicalReports/TR-INF-2011-06-01-UNIPMN.pdf">Spaced seeds design using perfect rulers</a>, Tech. Rep. CS Department Universita del Piemonte Orientale, June 2011. %H A193803 Peter Luschny, <a href="http://oeis.org/wiki/User:Peter_Luschny/PerfectRulers">Perfect rulers</a> %H A193803 B. Wichmann, <a href="http://jlms.oxfordjournals.org/content/s1-38/1/465.extract">A note on restricted difference bases</a>, J. Lond. Math. Soc. 38 (1963), 465-466. %e A193803 [0, 1, 2, 5, 10, 15, 26, 37, 48, 54, 60, 66, 67, 68] is a perfect Wichmann ruler with length 68 of Wichmann type (2,3). By contrast [0, 1, 2, 8, 15, 16, 26, 36, 46, 56, 59, 63, 65, 68] is a perfect ruler with length 68 which is not a Wichmann ruler. %Y A193803 Cf. A004137, A193802. %K A193803 nonn,hard,more %O A193803 1,1 %A A193803 _Peter Luschny_, Oct 22 2011