login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A128177 A128174 * A004736 as infinite lower triangular matrices. 0
1, 2, 1, 4, 2, 1, 6, 4, 2, 1, 9, 6, 4, 2, 1, 12, 9, 6, 4, 2, 1, 16, 12, 9, 6, 4, 2, 1, 20, 16, 12, 9, 6, 4, 2, 1, 25, 20, 16, 12, 9, 6, 4, 2, 1, 30, 25, 20, 16, 12, 9, 6, 4, 2, 1, 36, 30, 25, 20, 16, 12, 9, 6, 4, 2, 1, 42, 36, 30, 25, 20, 16, 12, 9, 6, 4, 2, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

n-th row has n nonzero terms of A002620: (1, 2, 4, 6, 9, 12, 16, ...) in reverse.

Row sums = A002623: (1, 3, 7, 13, 22, 34, 50, ...).

LINKS

Table of n, a(n) for n=1..78.

EXAMPLE

First few rows of the triangle are:

1;

2, 1;

4, 2, 1;

6, 4, 2, 1;

9, 6, 4, 2, 1;

12, 9, 6, 4, 2, 1;

...

PROG

(PARI) lista(nn) = {t128174 = matrix(nn, nn, n, k, (k<=n)*(1+(-1)^(n-k))/2); t004736 = matrix(nn, nn, n, k, (k<=n)*(n - k + 1)); t128177 = t128174*t004736; for (n = 1, nn, for (k = 1, n, print1(t128177[n, k], ", "); ); ); } \\ Michel Marcus, Feb 11 2014

CROSSREFS

Cf. A128174, A004736, A002623, A002620.

Sequence in context: A347069 A325309 A211956 * A087738 A133113 A124840

Adjacent sequences:  A128174 A128175 A128176 * A128178 A128179 A128180

KEYWORD

nonn,tabl

AUTHOR

Gary W. Adamson, Feb 17 2007

EXTENSIONS

Partially edited and more terms from Michel Marcus, Feb 11 2014

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 January 25 12:40 EST 2022. Contains 350572 sequences. (Running on oeis4.)