|
Search: id:A128213
|
|
|
| A128213 |
|
Expansion of (1-x+2x^2-2x^3)/(1-x+x^2)^2. |
|
+0
2
|
|
| 1, 1, 1, -1, -4, -4, 1, 7, 7, -1, -10, -10, 1, 13, 13, -1, -16, -16, 1, 19, 19, -1, -22, -22, 1, 25, 25, -1, -28, -28, 1, 31, 31, -1, -34, -34, 1, 37, 37, -1, -40, -40, 1, 43, 43, -1, -46, -46, 1, 49, 49
(list; graph; listen)
|
|
|
OFFSET
|
0,5
|
|
|
COMMENT
|
a(n+1) is the Hankel transform of {1,0,1,3,9,28,90,297,1001,3432,11934,...}, cf. A000245. Binomial transform of A128214.
a(n+2) is the Hankel transform of A014138. - Paul Barry (pbarry(AT)wit.ie), Mar 15 2008
|
|
FORMULA
|
a(n)=cos(pi*n/3)+(2n/sqrt(3)-1/sqrt(3))*sin(pin/3);
|
|
CROSSREFS
|
Sequence in context: A021878 A016495 A047213 this_sequence A016706 A138679 A080721
Adjacent sequences: A128210 A128211 A128212 this_sequence A128214 A128215 A128216
|
|
KEYWORD
|
easy,sign
|
|
AUTHOR
|
Paul Barry (pbarry(AT)wit.ie), Feb 19 2007
|
|
|
Search completed in 0.002 seconds
|
