|
Search: id:A090132
|
|
|
| A090132 |
|
Expansion of (1+2x)/(1+2x+2x^2). |
|
+0
6
|
|
| 1, 0, -2, 4, -4, 0, 8, -16, 16, 0, -32, 64, -64, 0, 128, -256, 256, 0, -512, 1024, -1024, 0, 2048, -4096, 4096, 0, -8192, 16384, -16384, 0, 32768, -65536, 65536, 0, -131072, 262144, -262144, 0, 524288, -1048576, 1048576, 0, -2097152, 4194304, -4194304, 0, 8388608
(list; graph; listen)
|
|
|
OFFSET
|
0,3
|
|
|
COMMENT
|
The expansion of (1-2x)/(1-2x+2x^2) has a(n)=sum{k=0..n, C(n,k)(-1)^(-k)(-1)^floor(k/2)}
|
|
FORMULA
|
a(n)=sum{k=0..n, C(n, k)(-1)^(n-k)(-1)^floor(k/2)}
a(n)=sqrt(2)*2^(n/2)sin(3*pi*n/4+pi/4) - Paul Barry (pbarry(AT)wit.ie), Feb 25 2004
a(n)=-a(n-1)+2a(n-3). - Paul Curtz (bpcrtz(AT)free.fr), Apr 24 2008
|
|
CROSSREFS
|
Cf. A009116.
Cf. A135353, A137444, A137426, A137429.
Sequence in context: A009116 A146559 A118434 this_sequence A099211 A094225 A057277
Adjacent sequences: A090129 A090130 A090131 this_sequence A090133 A090134 A090135
|
|
KEYWORD
|
easy,sign
|
|
AUTHOR
|
Paul Barry (pbarry(AT)wit.ie), Nov 21 2003
|
|
|
Search completed in 0.005 seconds
|
