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 A109977 #2 Mar 30 2012 18:59:08 %S A109977 1,-2,1,4,-3,1,-15,11,-5,1,107,-76,35,-9,1,-1475,1041,-476,125,-17,1, %T A109977 40914,-28858,13177,-3460,479,-33,1,-2327019,1641270,-749336,196731, %U A109977 -27260,1901,-65,1,271813931,-191712888,87527566,-22979242,3184213,-222196,7655,-129,1,-64930439315,45796039830 %N A109977 Inverse of number-theoretic triangle A109974. %e A109977 Rows begin %e A109977 1; %e A109977 -2,1; %e A109977 4,-3,1; %e A109977 -15,11,-5,1; %e A109977 107,-76,35,-9,1; %e A109977 -1475,1041,-476,125,-17,1; %K A109977 sign,tabl %O A109977 0,2 %A A109977 _Paul Barry_, Jul 06 2005