A238960 - OEIS

%I #19 Apr 25 2020 18:14:05

%S 0,0,1,2,1,3,6,2,5,6,10,16,2,6,8,14,16,26,40,3,8,11,12,18,23,27,36,42,

%T 64,96,3,9,13,15,22,29,32,37,46,58,67,88,102,152,224,4,11,16,19,20,26,

%U 36,41,48,52,56,74,80,93,108,112,140,162,208,240,352,512

%N The number of arcs from odd to even level vertices in divisor lattice in graded colexicographic order.

%H Andrew Howroyd, <a href="/A238960/b238960.txt">Table of n, a(n) for n = 0..2713</a> (rows 0..20)

%H 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, Table A.1 entry |E_O(S)|.

%F T(n,k) = A238951(A036035(n,k)).

%F From _Andrew Howroyd_, Apr 25 2020: (Start)

%F T(n,k) = floor(A238953(n,k)/2).

%F T(n,k) = A238953(n,k) - A238959(n,k). (End)

%e Triangle T(n,k) begins:

%e   0;

%e   0;

%e   1, 2;

%e   1, 3,  6;

%e   2, 5,  6, 10, 16;

%e   2, 6,  8, 14, 16, 26, 40;

%e   3, 8, 11, 12, 18, 23, 27, 36, 42, 64, 96;

%e   ...

%Y Cf. A238951 in graded colexicographic order.

%Y Cf. A036035, A238953, A238959, A238973.

%K nonn,tabf

%O 0,4

%A _Sung-Hyuk Cha_, Mar 07 2014

%E Offset changed and terms a(50) and beyond from _Andrew Howroyd_, Apr 25 2020