|
Search: id:A005726
|
|
|
| A005726 |
|
Quadrinomial coefficients.
(Formerly M1643)
|
|
+0
2
|
|
| 1, 2, 6, 20, 65, 216, 728, 2472, 8451, 29050, 100298, 347568, 1208220, 4211312, 14712960, 51507280, 180642391, 634551606, 2232223626, 7862669700, 27727507521, 97884558992, 345891702456, 1223358393120, 4330360551700
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
REFERENCES
|
L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 78.
|
|
FORMULA
|
a(n)=sum{k=0..floor(n/2), C(n, k)C(n, 2k+1) }. - Paul Barry (pbarry(AT)wit.ie), May 15 2003
a(n)=Sum[(-1)^k binomial[n,k] binomial[2n-2-4k,n-1],{k,0,Floor[(n-1)/4]}]. - David Callan (callan(AT)stat.wisc.edu), Jul 03 2006
|
|
MAPLE
|
for n from 1 to 40 do printf(`%d, `, coeff(expand(sum(x^j, j=0..3)^n), x, n-1)) od:
|
|
CROSSREFS
|
Adjacent sequences: A005723 A005724 A005725 this_sequence A005727 A005728 A005729
Sequence in context: A132353 A052958 A053730 this_sequence A000718 A027061 A083323
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
njas
|
|
EXTENSIONS
|
More terms from James A. Sellers (sellersj(AT)math.psu.edu), Aug 21 2000
|
|
|
Search completed in 0.002 seconds
|
