|
Search: id:A052141
|
|
|
| A052141 |
|
Number of paths from (0,0) to (n,n) that always move closer to (n,n) (and do not pass (n,n) and backtrack). |
|
+0
4
|
|
| 1, 3, 26, 252, 2568, 26928, 287648, 3112896, 34013312, 374416128, 4145895936, 46127840256, 515268544512, 5775088103424, 64912164888576, 731420783788032, 8259345993203712, 93443504499523584, 1058972245409005568, 12019152955622817792
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
REFERENCES
|
R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Example 6.3.9.
|
|
FORMULA
|
G.f.: 1/2+1/(2*(1-12*x+4*x^2)^(1/2)).
a(n) = A001850(n)*2^(n-1) - Jon Stadler (jstadler(AT)capital.edu), Apr 30 2003
|
|
CROSSREFS
|
Main diagonal of A059576.
Cf. A084773.
Sequence in context: A037797 A071846 A067858 this_sequence A062793 A048861 A053972
Adjacent sequences: A052138 A052139 A052140 this_sequence A052142 A052143 A052144
|
|
KEYWORD
|
nonn,easy,nice,walk
|
|
AUTHOR
|
njas, Jan 23 2000
|
|
|
Search completed in 0.002 seconds
|
