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A080772
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Numbers of numbers <= n having prime factors <= k, triangular array read by rows.
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0
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1, 1, 2, 1, 2, 3, 1, 2, 4, 4, 1, 2, 4, 4, 5, 1, 2, 4, 4, 6, 6, 1, 2, 4, 4, 6, 6, 7, 1, 2, 4, 4, 6, 6, 8, 8, 1, 2, 4, 4, 6, 6, 9, 9, 9, 1, 2, 4, 4, 6, 6, 10, 10, 10, 10, 1, 2, 4, 4, 6, 6, 10, 10, 10, 10, 11, 1, 2, 4, 4, 6, 6, 10, 10, 10, 10, 12, 12, 1, 2, 4, 4, 6, 6, 10, 10, 10, 10, 12, 12, 13, 1, 2, 4, 4
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| T(n,k) = #{m: 1<=m<=n and p<=k for prime factors of m}.
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FORMULA
| T(n, n)=n and T(n, k-1) = if k is prime then k-1 else T(n, k), 1<k<=n.
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EXAMPLE
| Triangle begins:
................. 1
............... 1...2
............. 1...2...3
........... 1...2...4...4
......... 1...2...4...4...5
....... 1...2...4...4...6...6
..... 1...2...4...4...6...6...7
... 1...2...4...4...6...6...8...8.
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CROSSREFS
| Sequence in context: A194914 A195076 A163491 * A145111 A104795 A116925
Adjacent sequences: A080769 A080770 A080771 * A080773 A080774 A080775
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KEYWORD
| nonn,tabl
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 10 2003
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