A138553 - OEIS

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A138553

Table read by rows: T(n,k) is the number of divisors of k that are <= n.

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

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]

LINKS

Table of n, a(n) for n=1..105.

FORMULA

T(n,k) = sum_{i|k, i<=n} 1.

EXAMPLE

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]

PROG

(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

CROSSREFS

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

KEYWORD

easy,nonn,tabf

AUTHOR

Franklin T. Adams-Watters, Mar 24 2008

EXTENSIONS

Definition corrected by Franklin T. Adams-Watters, Jun 19 2014

STATUS

approved