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A238689 Table read by rows: first row is {1}; for n >1, T(n, k) is the k-th largest prime factor of n (repeated prime factors are counted repeatedly). 2
1, 2, 3, 2, 2, 5, 3, 2, 7, 2, 2, 2, 3, 3, 5, 2, 11, 3, 2, 2, 13, 7, 2, 5, 3, 2, 2, 2, 2, 17, 3, 3, 2, 19, 5, 2, 2, 7, 3, 11, 2, 23, 3, 2, 2, 2, 5, 5, 13, 2, 3, 3, 3, 7, 2, 2, 29, 5, 3, 2, 31, 2, 2, 2, 2, 2, 11, 3, 17, 2, 7, 5, 3, 3, 2, 2, 37, 19, 2, 13, 3, 5, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

n-th row has length 1 if n = 1, A001222(n) if n > 1.

LINKS

Peter Kagey, Table of n, a(n) for n = 1..10000

FORMULA

Row n is row n of A027746 in reverse order.

EXAMPLE

Table begins:

1;

2;

3;

2,2;

5;

3,2;

7;

2,2,2;

3,3;

5,2;

...

PROG

(Haskell)

a238689_row 1 = [1]

a238689_row n = a n [] a000040_list where

  a m factors ps@(p:ps')

    | m == 1         = factors

    | m `mod` p == 0 = a (m `div` p) (p : factors) ps

    | otherwise      = a m           factors       ps'

a _ _ [] = [] -- Peter Kagey, Sep 15 2016

CROSSREFS

First column is A006530; numbers along right boundary form A020639.

A001414 gives row sums (for n > 1).

Cf. A027746, A238690.

Sequence in context: A207338 A027746 A240230 * A166454 A283239 A128651

Adjacent sequences:  A238686 A238687 A238688 * A238690 A238691 A238692

KEYWORD

nonn,tabf

AUTHOR

Matthew Vandermast, Apr 28 2014

STATUS

approved

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Last modified December 13 19:20 EST 2017. Contains 295976 sequences.