|
| |
|
|
A154990
|
|
Triangle read by rows. Main diagonal is positive. The rest of the terms are negative.
|
|
7
|
|
|
|
1, -1, 1, -1, -1, 1, -1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 1, -1, -1, -1, -1, -1, -1, -1
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Triangle can be used in matrix inverses. Signs in columns as in A153881.
Iff n is a triangular number, a(n)=1; otherwise, a(n)=-1. (This is explicitly implemented in the second Mathematica program below.) - Harvey P. Dale, Apr 27 2014
|
|
|
LINKS
|
Table of n, a(n) for n=1..73.
|
|
|
EXAMPLE
|
Table begins:
1;
-1,1;
-1,-1,1;
-1,-1,-1,1;
-1,-1,-1,-1,1;
-1,-1,-1,-1,-1,1;
-1,-1,-1,-1,-1,-1,1;
|
|
|
MAPLE
|
(Excel) =if(row()>=column(); if(row()>=column(); 1; "")*if(row()>column(); -1; 1); "")
|
|
|
MATHEMATICA
|
Flatten[Table[PadLeft[{1}, n, -1], {n, 15}]] (* or *) With[{tr=Accumulate[ Range[ 15]]}, Table[If[MemberQ[tr, n], 1, -1], {n, Last[tr]}]] (* Harvey P. Dale, Apr 27 2014 *)
|
|
|
CROSSREFS
|
Sequence in context: A160357 A057077 A070748 * A209615 A156734 A119664
Adjacent sequences: A154987 A154988 A154989 * A154991 A154992 A154993
|
|
|
KEYWORD
|
sign,easy,tabl
|
|
|
AUTHOR
|
Mats Granvik, Jan 18 2009
|
|
|
STATUS
|
approved
|
| |
|
|
