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 A173865 #2 Mar 30 2012 18:52:39 %S A173865 1,5,35,7,25,49,11,65,77,143,13,55,91,121,169,17,95,119,209,221,323, %T A173865 19,65,133,187,247,289,361,23,125,161,275,299,425,437,575,25,115,175, %U A173865 253,325,391,475,529,625,29,155,203,341,377,527,589,713,725,899,31,145,217 %N A173865 Alternating triangle read by rows: numbers k such that k=6*m+-1=r*j, r>=j and n>=q where r=6*n-1 or r=6*n+1 and j=6*q-1 or j=6*q+1. %C A173865 Numbers of form 6*m+1 are in even rows, numbers of form 6*m-1 are in odd rows. %e A173865 Triangle begins: 1*1 5*1 7*5 7*1 5*5 7*7 11*1 13*5 11*7 13*11 13*1 11*5 13*7 11*11 13*13 17*1 19*15 17*7 19*11 17*13 19*17 19*1 17*5 19*7 17*11 19*13 17*17 19*19.. or 1(in even 0 row) 5 35(in odd 1 row) 7 25 49(in even 2 row) 11 65 77 143(in odd 3 row) 13 55 91 121 169(in even 4 row) 17 95 119 209 221 323(in odd 5 row) 19 65 133 187 247 289 361(in even 6 row).. %Y A173865 Cf. A007310, A173825. %K A173865 nonn,tabl %O A173865 1,2 %A A173865 _Juri-Stepan Gerasimov_, Feb 26 2010, Mar 06 2010