|
Search: id:A095817
|
|
|
| A095817 |
|
Number of permutations of 1..n with no four elements in correct or reverse order. |
|
+0
3
|
|
| 1, 2, 6, 22, 114, 692, 4884, 39318, 355490, 3567292, 39345804, 473148014, 6161310442, 86376341412, 1297099489668, 20772929663254, 353415786538434, 6365693021157116, 121016486728717740
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
For no n do either of the subsequences n(n+1)(n+2)(n+3) or (n+3)(n+2)(n+1)n occur in any permutation.
|
|
LINKS
|
Jackson, D. M. and Read, R. C., A note on permutations without runs of given length, Aequationes Math. 17 (1978), no. 2-3, 336-343.
|
|
FORMULA
|
G.f. for number of permutations of 1..n with no m elements in correct or reverse order is Sum(n!*((2*x^m-x^(m+1)-x)/(x^m-1))^n,n=0..infinity). - Ivana Jovovic ( ivana121(AT)EUnet.yu ), Nov 11 2007
|
|
CROSSREFS
|
Cf. A002464, A095816, A095818.
Sequence in context: A129535 A014371 A111280 this_sequence A101042 A032266 A095856
Adjacent sequences: A095814 A095815 A095816 this_sequence A095818 A095819 A095820
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Jonas Wallgren (jonwa(AT)ida.liu.se), Jun 08 2004
|
|
EXTENSIONS
|
More terms from Ivana Jovovic ( ivana121(AT)EUnet.yu ), Nov 11 2007
|
|
|
Search completed in 0.002 seconds
|
