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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A127949 A000012 as an infinite lower triangular matrix with all 1's; A127899 = a simple transform; then A000012 * A127899. Given A051340, change all 1's to -1. Triangle read by rows, (n-1) -1's followed by "n". 3
1, -1, 2, -1, -1, 3, -1, -1, -1, 4, -1, -1, -1, -1, 5, -1, -1, -1, -1, -1, 6, -1, -1, -1, -1, -1, -1, 7, -1, -1, -1, -1, -1, -1, -1, 8, -1, -1, -1, -1, -1, -1, -1, -1, 9, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 11, -1, -1, -1, -1, -1, -1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

For the inverse of A127949 see A126615, a harmonic triangle.

This is one way to define an inverse to A000217. - R. J. Mathar, Apr 30 2010

LINKS

Table of n, a(n) for n=1..72.

EXAMPLE

First few rows of the triangle are:

1;

-1, 2;

-1, -1, 3;

-1, -1, -1, 4;

...

MAPLE

A127949 := proc(n) if issqr(1+8*n) then (sqrt(1+8*n)-1)/2 ; else -1 ; end if; end proc: seq(A127949(n), n=1..120) ; # R. J. Mathar, Apr 30 2010

CROSSREFS

Cf. A000012, A127899, A051340, A126615.

Sequence in context: A196931 A175465 A080209 * A167407 A051340 A216764

Adjacent sequences:  A127946 A127947 A127948 * A127950 A127951 A127952

KEYWORD

tabl,sign,easy

AUTHOR

Gary W. Adamson, Feb 09 2007

EXTENSIONS

More terms from R. J. Mathar, Apr 30 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 March 23 02:57 EDT 2019. Contains 321422 sequences. (Running on oeis4.)