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 A173800 #5 Mar 30 2012 17:22:55 %S A173800 1,4,13,10,40,121,28,91,364,1093,82,328,820,3280,757,9841,244,7381, %T A173800 29524,88573,730,949,2920,6643,9490,20440,26572,66430,265720,797161, %U A173800 2188,597871,2391484,59293,551881,7174453,6562,26248,65620,253216 %N A173800 Irregular triangle in which row n has primitive numbers k such that 1/k is in the Cantor set and the fraction 1/k has period n. %C A173800 This sequence is a permutation of A173793. Row n ends with (3^n-1)/2. The length of row n is A173801(n). %H A173800 T. D. Noe, <a href="/A173800/b173800.txt">Rows n=1..200, flattened</a> %K A173800 nonn,tabf %O A173800 1,2 %A A173800 _T. D. Noe_, Feb 25 2010