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A295908
Triangle in which n-th row lists divisors d of n such that n/d is squarefree.
0
1, 1, 2, 1, 3, 2, 4, 1, 5, 1, 2, 3, 6, 1, 7, 4, 8, 3, 9, 1, 2, 5, 10, 1, 11, 2, 4, 6, 12, 1, 13, 1, 2, 7, 14, 1, 3, 5, 15, 8, 16, 1, 17, 3, 6, 9, 18, 1, 19, 2, 4, 10, 20, 1, 3, 7, 21, 1, 2, 11, 22, 1, 23, 4, 8, 12, 24, 5, 25, 1, 2, 13, 26, 9, 27, 2, 4, 14, 28
OFFSET
1,3
COMMENTS
For any n > 0:
- the n-th row has A034444(n) terms,
- the n-th row has sum A001615(n),
- the n-th row has leading term A003557(n).
FORMULA
T(n, k) = n / A206778(n, A034444(n) - k + 1) for any n > 0 and k such that 1 <= k <= A034444(n).
EXAMPLE
Triangle begins:
1: [1]
2: [1, 2]
3: [1, 3]
4: [2, 4]
5: [1, 5]
6: [1, 2, 3, 6]
7: [1, 7]
8: [4, 8]
9: [3, 9]
10: [1, 2, 5, 10]
11: [1, 11]
12: [2, 4, 6, 12]
13: [1, 13]
14: [1, 2, 7, 14]
15: [1, 3, 5, 15]
16: [8, 16]
17: [1, 17]
18: [3, 6, 9, 18]
19: [1, 19]
20: [2, 4, 10, 20]
PROG
(PARI) for (n=1, 28, fordiv (n, d, if (issquarefree(n/d), print1 (d ", "))))
CROSSREFS
Cf. A001615 (row sums), A003557, A005117, A034444 (row lengths), A206778.
Sequence in context: A124223 A377027 A379730 * A300980 A260429 A094193
KEYWORD
nonn,tabf
AUTHOR
Rémy Sigrist, Nov 29 2017
STATUS
approved