A238960 The number of arcs from odd to even level vertices in divisor lattice in graded colexicographic order.

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, 64, 96, 3, 9, 13, 15, 22, 29, 32, 37, 46, 58, 67, 88, 102, 152, 224, 4, 11, 16, 19, 20, 26, 36, 41, 48, 52, 56, 74, 80, 93, 108, 112, 140, 162, 208, 240, 352, 512

Offset

0,4

Links

Andrew Howroyd, Table of n, a(n) for n = 0..2713 (rows 0..20)

S.-H. Cha, E. G. DuCasse, and L. V. Quintas, Graph Invariants Based on the Divides Relation and Ordered by Prime Signatures, arXiv:1405.5283 [math.NT], 2014, Table A.1 entry |E_O(S)|.

Formula

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

From Andrew Howroyd, Apr 25 2020: (Start)

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

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

Example

Triangle T(n,k) begins:
  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, 64, 96;
  ...

Crossrefs

Cf. A238951 in graded colexicographic order.

Cf. A036035, A238953, A238959, A238973.

Sequence in context: A145888 A213935 A106578 * A238973 A335444 A358646

Adjacent sequences: A238957 A238958 A238959 * A238961 A238962 A238963

Keyword

nonn,tabf

Author

Sung-Hyuk Cha, Mar 07 2014

Extensions

Offset changed and terms a(50) and beyond from Andrew Howroyd, Apr 25 2020

Status

approved