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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A181415 Irregular triangle a(n,k) = A049009(n,k)/n, read by rows 1<=k<=A000041(n). 1
1, 1, 1, 1, 6, 2, 1, 12, 9, 36, 6, 1, 20, 40, 120, 180, 240, 24, 1, 30, 75, 50, 300, 1200, 300, 1200, 2700, 1800, 120, 1, 42, 126, 210, 630, 3150, 2100, 3150, 4200, 25200, 12600, 12600, 37800, 15120, 720, 1, 56, 196, 392, 245, 1176, 7056, 11760, 8820, 11760, 11760, 88200 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Table of n, a(n) for n=1..56.

FORMULA

Sum_{k=1.. A000041(n)} a(n,k) = A000169(n). (Row sums)

a(n,k) = A098546(n,k) *A049019(n,k) /n. - Compare with the formula in A101818.

EXAMPLE

Row three is calculated as follows:

( 3 18 6) divided by (3 3 3) yielding (1 6 2)

1;

1,1;

1,6,2;

1,12,9,36,6;

1,20,40,120,180,240,24;

1,30,75,50,300,1200,300,1200,2700,1800,120;

1,42,126,210,630,3150,2100,3150,4200,25200,12600,12600,37800,15120,720;

CROSSREFS

Cf. A000169 (row sums), A000081 (unlabeled rooted trees) A179438 (a similar refinement), A054589, A135278, A019538, A101817, A101818

Sequence in context: A217909 A002247 A124913 * A289711 A101818 A138186

Adjacent sequences:  A181412 A181413 A181414 * A181416 A181417 A181418

KEYWORD

nonn,tabf

AUTHOR

Alford Arnold, Oct 20 2010

EXTENSIONS

Edited by R. J. Mathar, May 17 2016

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 October 23 11:19 EDT 2019. Contains 328345 sequences. (Running on oeis4.)