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A138553
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Table read by rows: T(n,k) is the number of divisors of k that are <= n.
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2
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1, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 2, 3, 1, 3, 1, 3, 2, 2, 1, 4, 1, 2, 2, 3, 2, 3, 1, 3, 2, 3, 1, 4, 1, 2, 3, 3, 1, 3, 1, 4, 2, 2, 1, 4, 2, 2, 2, 3, 1, 4, 1, 3, 2, 2, 2, 4, 1, 2, 2, 4, 1, 3, 1, 3, 3, 2, 1, 4, 1, 3, 2, 3, 1, 3, 2, 3, 2, 2, 1, 5, 1, 2, 2, 3, 2, 4, 1, 3, 2, 3, 1, 5, 1, 2, 3, 3, 1, 4, 1, 4, 2, 2, 1, 5
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OFFSET
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1,3
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COMMENTS
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Suggested by a question from Eric Desbiaux.
The row lengths are the lengths before the pattern for n repeats.
Antidiagonal sums A070824. [From Eric Desbiaux, Dec 10 2009]
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LINKS
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Table of n, a(n) for n=1..105.
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FORMULA
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T(n,k) = sum_{i|k, i<=n} 1.
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EXAMPLE
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The first few rows start:
1, [A000012]
1, 2, [A000034]
1, 2, 2, 2, 1, 3, [A083039]
1, 2, 2, 3, 1, 3, 1, 3, 2, 2, 1, 4, [A083040]
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PROG
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(PARI) lista(nrows) = {for (n=1, nrows, for (k=1, lcm(vector(n, i, i)), print1(sumdiv(k, d, d <=n), ", "); ); print(); ); } \\ Michel Marcus, Jun 19 2014
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CROSSREFS
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Row lengths A003418, row sums A025529, frequencies in rows A096180.
Cf. A243987
Sequence in context: A334507 A342462 A239140 * A069016 A211270 A071414
Adjacent sequences: A138550 A138551 A138552 * A138554 A138555 A138556
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KEYWORD
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easy,nonn,tabf
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AUTHOR
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Franklin T. Adams-Watters, Mar 24 2008
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EXTENSIONS
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Definition corrected by Franklin T. Adams-Watters, Jun 19 2014
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STATUS
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approved
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