|
Search: id:A108476
|
|
|
| A108476 |
|
Expansion of (1-4x)/(1-6x-12x^2+8x^3). |
|
+0
1
|
|
| 1, 2, 24, 160, 1232, 9120, 68224, 508928, 3799296, 28357120, 211662848, 1579868160, 11792306176, 88018952192, 656982441984, 4903783628800, 36602339459072, 273203580764160, 2039219289063424, 15220939987877888
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
COMMENT
|
In general, sum{k=0..n, sum{j=0..n, C(2(n-k),j)C(2k,j)r^j}} has expansion (1-(r+1)x)/((1+(r+3)x+(r-1)(r+3)x^2+(r-1)^3*x^3).
|
|
FORMULA
|
G.f.: (1-4x)/((1+2x)(1-8x+4x^2)); a(n)=6a(n-1)+12a(n-2)-8a(n-3); a(n)=sum{k=0..n, sum{j=0..n, C(2(n-k), j)C(2k, j)3^j}}.
|
|
CROSSREFS
|
Sequence in context: A000185 A035600 A013528 this_sequence A052411 A073066 A002736
Adjacent sequences: A108473 A108474 A108475 this_sequence A108477 A108478 A108479
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Paul Barry (pbarry(AT)wit.ie), Jun 04 2005
|
|
|
Search completed in 0.002 seconds
|
