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 A238959 #18 Apr 25 2020 18:13:19 %S A238959 0,1,1,2,2,4,6,2,5,6,10,16,3,7,9,14,17,26,40,3,8,11,12,18,23,27,36,42, %T A238959 64,96,4,10,14,16,22,30,32,38,46,58,68,88,102,152,224,4,11,16,19,20, %U A238959 26,36,41,48,52,56,74,80,93,108,112,140,162,208,240,352,512 %N A238959 The number of arcs from even to odd level vertices in divisor lattice in graded colexicographic order. %H A238959 Andrew Howroyd, <a href="/A238959/b238959.txt">Table of n, a(n) for n = 0..2713</a> (rows 0..20) %H A238959 S.-H. Cha, E. G. DuCasse, and L. V. Quintas, <a href="http://arxiv.org/abs/1405.5283">Graph Invariants Based on the Divides Relation and Ordered by Prime Signatures</a>, arxiv:1405.5283 [math.NT], 2014. %F A238959 T(n,k) = A238950(A036035(n,k)). %F A238959 From _Andrew Howroyd_, Apr 25 2020: (Start) %F A238959 T(n,k) = ceiling(A238953(n,k)/2). %F A238959 T(n,k) = A238953(n,k) - A238960(n,k). (End) %e A238959 Triangle T(n,k) begins: %e A238959 0; %e A238959 1; %e A238959 1, 2; %e A238959 2, 4, 6; %e A238959 2, 5, 6, 10, 16; %e A238959 3, 7, 9, 14, 17, 26, 40; %e A238959 3, 8, 11, 12, 18, 23, 27, 36, 42, 64, 96; %e A238959 ... %Y A238959 Cf. A238950 in graded colexicographic order. %Y A238959 Cf. A036035, A238953, A238960, A238972. %K A238959 nonn,tabf %O A238959 0,4 %A A238959 _Sung-Hyuk Cha_, Mar 07 2014 %E A238959 Offset changed and terms a(50) and beyond from _Andrew Howroyd_, Apr 25 2020