|
Search: id:A063020
|
|
|
| A063020 |
|
Reversion of y - y^2 - y^3 + y^4. |
|
+0
3
|
|
| 0, 1, 1, 3, 9, 32, 119, 466, 1881, 7788, 32868, 140907, 611871, 2685732, 11896906, 53115412, 238767737, 1079780412, 4909067468, 22424085244, 102865595140, 473678981820, 2188774576575, 10145798119530, 47165267330415
(list; graph; listen)
|
|
|
OFFSET
|
0,4
|
|
|
COMMENT
|
Seems to be the inverse of A007858. Can someone prove this?
a(n+1) counts paths from (0,0) to (n,n) which do not go above the line y=x, using steps (1,0) and (2k,1), where k ranges over the nonnegative integers. For example, the 9 paths from (0,0) to (3,3) are the 5 Catalan paths, as well as DNEN, DENN, EDNN, and ENDN. Here E=(1,0), N=(0,1), D=(2,1). - Brian Drake (bdrake(AT)brandeis.edu), Sep 20 2007
|
|
LINKS
|
Index entries for reversions of series
|
|
MAPLE
|
A:= series(RootOf(_Z-_Z^2-_Z^3+_Z^4-x), x, 21): seq(coeff(A, x, i), i=0..20); - Brian Drake (bdrake(AT)brandeis.edu), Sep 20 2007
|
|
MATHEMATICA
|
CoefficientList[InverseSeries[Series[y - y^2 - y^3 + y^4, {y, 0, 30}], x], x]
|
|
CROSSREFS
|
Cf. A007848.
Cf. A052709, A064641.
Sequence in context: A052872 A122452 A091841 this_sequence A104184 A039628 A005964
Adjacent sequences: A063017 A063018 A063019 this_sequence A063021 A063022 A063023
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
Olivier Gerard (ogerard(AT)ext.jussieu.fr), Jul 05 2001.
|
|
|
Search completed in 0.002 seconds
|
