|
Search: id:A138265
|
|
|
| A138265 |
|
Number of upper triangular zero-one matrices with n ones and no zero rows or columns. |
|
+0
5
|
|
| 1, 1, 1, 2, 5, 16, 61, 271, 1372, 7795, 49093, 339386, 2554596, 20794982, 182010945, 1704439030, 17003262470, 180011279335, 2015683264820, 23801055350435, 295563725628564, 3850618520827590, 52514066450469255
(list; graph; listen)
|
|
|
OFFSET
|
0,4
|
|
|
FORMULA
|
G.f.: Sum(Product(1-1/(1+x)^i,i=1..n),n=0..infinity).
a(n) = (1/n!)*Sum_{k=0..n} Stirling1(n,k)*A079144(k). a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n-1,k-1)*A022493(k).
|
|
MAPLE
|
g:=sum(product(1-1/(1+x)^i, i=1..n), n=0..35): gser:=series(g, x=0, 30): seq(coeff(gser, x, n), n=0..22); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 23 2008
|
|
CROSSREFS
|
Cf. A005321, A104602, A135588.
Sequence in context: A012159 A009736 A104858 this_sequence A000111 A163747 A007976
Adjacent sequences: A138262 A138263 A138264 this_sequence A138266 A138267 A138268
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 10 2008, Mar 11 2008
|
|
EXTENSIONS
|
More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 23 2008
|
|
|
Search completed in 0.002 seconds
|
