login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A207018 Number of permutations in S_n with major index equal to inversion number. 1
1, 2, 4, 10, 28, 116, 576, 3634, 26620, 223440, 2100964, 21888712, 250062982, 3108430640 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
At first equal to and eventually greater than corresponding entry of A195924, number of fixed points of Foata's bijection.
For any large n, the two permutations with maj and inv both 2 are 2314..n, and 14235..n.
LINKS
EXAMPLE
A(4)=10: the 10 permutations of 4 elements with major index equal to inversion number are
#: perm #inv. inversion table
1: [ 0 1 2 3 ] 0 [ 0 0 0 ]
2: [ 0 3 1 2 ] 2 [ 0 2 0 ]
3: [ 1 0 2 3 ] 1 [ 0 0 1 ]
4: [ 1 2 0 3 ] 2 [ 0 1 1 ]
5: [ 1 2 3 0 ] 3 [ 1 1 1 ]
6: [ 2 1 0 3 ] 3 [ 0 1 2 ]
7: [ 2 1 3 0 ] 4 [ 1 1 2 ]
8: [ 2 3 1 0 ] 5 [ 1 2 2 ]
9: [ 3 0 2 1 ] 4 [ 1 0 3 ]
10: [ 3 2 1 0 ] 6 [ 1 2 3 ]
CROSSREFS
Cf. A195924.
Sequence in context: A022492 A352068 A123429 * A006841 A003223 A061417
KEYWORD
nonn,hard,more
AUTHOR
William J. Keith, Feb 14 2012
EXTENSIONS
a(14) by Joerg Arndt, Sep 29 2012.
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 07:27 EDT 2024. Contains 371265 sequences. (Running on oeis4.)