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A238959
The number of arcs from even to odd level vertices in divisor lattice in graded colexicographic order.
3
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, 64, 96, 4, 10, 14, 16, 22, 30, 32, 38, 46, 58, 68, 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.
FORMULA
T(n,k) = A238950(A036035(n,k)).
From Andrew Howroyd, Apr 25 2020: (Start)
T(n,k) = ceiling(A238953(n,k)/2).
T(n,k) = A238953(n,k) - A238960(n,k). (End)
EXAMPLE
Triangle T(n,k) begins:
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, 64, 96;
...
CROSSREFS
Cf. A238950 in graded colexicographic order.
Sequence in context: A113463 A278217 A191674 * A238972 A207193 A319579
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