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A319135
Irregular triangle read by rows in which row n lists the positive divisors of n that are <= sqrt(n) in decreasing order.
0
1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 1, 3, 2, 1, 1, 2, 1, 3, 1, 4, 2, 1, 1, 3, 2, 1, 1, 4, 2, 1, 3, 1, 2, 1, 1, 4, 3, 2, 1, 5, 1, 2, 1, 3, 1, 4, 2, 1, 1, 5, 3, 2, 1, 1, 4, 2, 1, 3, 1, 2, 1, 5, 1, 6, 4, 3, 2, 1, 1, 2, 1, 3, 1, 5, 4, 2, 1, 1, 6, 3, 2, 1
OFFSET
1,4
COMMENTS
Reversing rows gives A161906.
FORMULA
a(n) * A161908(n) = A340792(n)
A161906(n) * A340791(n) = A340792(n)
A027750(n) * A056538(n) = A061017(n)
EXAMPLE
Triangle begins:
1
1
1
2 1
1
2 1
1
2 1
3 1
2 1
1
3 2 1
1
2 1
3 1
4 2 1
PROG
(PARI) row(n) = Vecrev(select(x->(x<=sqrt(n)), divisors(n))); \\ Jinyuan Wang, Mar 13 2021
CROSSREFS
Cf. A038548 (row widths), A033676 (first column), A333750 (second column), A161906 (rows reversed), A027750, A056538, A061017, A340791, A340792.
Sequence in context: A254434 A076845 A161906 * A338884 A204901 A016014
KEYWORD
nonn,tabf
AUTHOR
Charles Kusniec, Feb 27 2021
EXTENSIONS
More terms from Jinyuan Wang, Mar 13 2021
STATUS
approved