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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A173997 Irregular triangular by columns derived from (1, 2, 3,...) * (1, 2, 3,...). 2
1, 2, 3, 2, 4, 4, 5, 6, 3, 6, 8, 6, 7, 10, 9, 4, 8, 12, 12, 8, 9, 14, 15, 12, 5, 10, 16, 18, 16, 10, 11, 18, 21, 20, 15, 6, 12, 20, 24, 24, 20, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row sums = A006918: (1, 2, 5, 8, 14, 20, 30,...).

LINKS

Table of n, a(n) for n=1..42.

FORMULA

Given a (1, 2, 3,...) * (1, 2, 3,...) multiplication table; leftmost column

of the triangle = (1, 2, 3,...). Then shift down each successive column of

the array twice to get triangle A173997.

EXAMPLE

Given:

...

1,..2,..3,..4,..5,...

2,..4,..6,..8,.10,...

3,..6,..9,.12,.15,...

4,..8,.12,.16,.20,...

...

After the shift twice operation, we obtain:

...

1;

2;

3, 2;

4, 4;

5, 6, 3;

6, 8, 6;

7, 10, 9, 4;

8, 12, 12, 8;

9, 14, 15, 12, 5;

10, 16, 18, 16, 10;

11, 18, 21, 20, 15, 6;

12, 20, 24, 24, 20, 12;

...

CROSSREFS

Cf. A006918

Sequence in context: A145394 A179806 A182762 * A029143 A153846 A284383

Adjacent sequences:  A173994 A173995 A173996 * A173998 A173999 A174000

KEYWORD

nonn,tabf

AUTHOR

Gary W. Adamson, Mar 05 2010

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 13 03:41 EST 2019. Contains 329968 sequences. (Running on oeis4.)