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A364884
Triangle T(n, k), n > 0, k = 1..n, read by rows; T(1, 1) = 1, and for n > 1, k = 1..n, T(n, k) is the least unseen multiple of the k-th term of the flattened sequence .
5
1, 2, 4, 3, 6, 8, 5, 10, 12, 9, 7, 14, 16, 15, 18, 11, 20, 24, 21, 30, 32, 13, 22, 28, 27, 36, 40, 25, 17, 26, 44, 33, 42, 48, 35, 50, 19, 34, 52, 39, 54, 56, 45, 60, 72, 23, 38, 64, 51, 66, 80, 55, 70, 84, 63, 29, 46, 68, 57, 78, 88, 65, 90, 96, 81, 49
OFFSET
1,2
COMMENTS
In other words, T(n, k) is a multiple of a(k).
As a flat sequence, this is a permutation of the positive integers (as each row starts with the least positive integer not yet in the sequence); see A364887 for the inverse permutation.
EXAMPLE
Triangle begins:
1,
2, 4
3, 6, 8
5, 10, 12, 9
7, 14, 16, 15, 18
11, 20, 24, 21, 30, 32
13, 22, 28, 27, 36, 40, 25
17, 26, 44, 33, 42, 48, 35, 50
19, 34, 52, 39, 54, 56, 45, 60, 72
23, 38, 64, 51, 66, 80, 55, 70, 84, 63
29, 46, 68, 57, 78, 88, 65, 90, 96, 81, 49
31, 58, 76, 69, 102, 104, 75, 100, 108, 99, 77, 98
..................................................
a(k) 1, 2, 4, 3, 6, 8, 5, 10, 12, 9, 7, 14
PROG
(PARI) See Links section.
CROSSREFS
See A361748 and A364885 for similar sequences.
Cf. A364887 (inverse).
Sequence in context: A358267 A280866 A280864 * A369825 A266411 A264740
KEYWORD
nonn,tabl
AUTHOR
Rémy Sigrist, Aug 12 2023
STATUS
approved