login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A141809 Irregular table: Row n (of A001221(n) terms, for n>=2) consists of the largest powers that divides n of each distinct prime that divides n. Terms are arranged by the size of the distinct primes. Row 1 = (1). 20
1, 2, 3, 4, 5, 2, 3, 7, 8, 9, 2, 5, 11, 4, 3, 13, 2, 7, 3, 5, 16, 17, 2, 9, 19, 4, 5, 3, 7, 2, 11, 23, 8, 3, 25, 2, 13, 27, 4, 7, 29, 2, 3, 5, 31, 32, 3, 11, 2, 17, 5, 7, 4, 9, 37, 2, 19, 3, 13, 8, 5, 41, 2, 3, 7, 43, 4, 11, 9, 5, 2, 23, 47, 16, 3, 49, 2, 25, 3, 17, 4, 13, 53, 2, 27, 5, 11, 8, 7, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

In other words, except for row 1, row n contains the unitary prime power divisors of n, sorted by the prime. - Franklin T. Adams-Watters, May 05 2011

A034684(n) = smallest term of n-th row; A028233(n) = T(n,1); A053585(n) = T(n,A001221(n)); A008475(n) = sum of n-th row for n > 1. - Reinhard Zumkeller, Jan 29 2013

LINKS

Reinhard Zumkeller, Rows n=1..10000 of triangle, flattened

Eric Weisstein's World of Mathematics, Prime Factorization

FORMULA

T(n,k) = A027748(n,k)^A124010(n,k) for n > 1, k = 1 .. A001221(n). - Reinhard Zumkeller, Mar 15 2012

EXAMPLE

60 has the prime factorization 2^2 * 3^1 * 5^1, so row 60 is (4,3,5).

From M. F. Hasler, Oct 12 2018: (Start)

The table starts:

   n : largest prime powers dividing n

   1 : 1

   2 : 2

   3 : 3

   4 : 4

   5 : 5

   6 : 2, 3

   7 : 7

   8 : 8

   9 : 9

   10 : 2, 5

   11 : 11

   12 : 4, 3

   etc. (End)

MATHEMATICA

f[{x_, y_}] := x^y; Table[Map[f, FactorInteger[n]], {n, 1, 50}] // Grid (* Geoffrey Critzer, Apr 03 2015 *)

PROG

(Haskell)

a141809 n k = a141809_row n !! (k-1)

a141809_row 1 = [1]

a141809_row n = zipWith (^) (a027748_row n) (a124010_row n)

a141809_tabf = map a141809_row [1..]

-- Reinhard Zumkeller, Mar 18 2012

(PARI) A141809_row(n)=if(n>1, apply(factorback, Col(factor(n)))~, [1]) \\ M. F. Hasler, Oct 12 2018

CROSSREFS

Cf. A141810, A027748.

Sequence in context: A161768 A213925 A141810 * A043265 A194459 A143120

Adjacent sequences:  A141806 A141807 A141808 * A141810 A141811 A141812

KEYWORD

nonn,tabf

AUTHOR

Leroy Quet, Jul 07 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 17 14:50 EST 2018. Contains 318201 sequences. (Running on oeis4.)