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!)
A208651 Number of paths through the subset array whose trace is a permutation of (1,2,...,n); see Comments. 2
1, 2, 12, 216, 11520, 1800000, 816480000, 1067311728000, 3996990937497600, 42672954793151692800, 1293547461212160000000000, 110950032218933108678400000000, 26847804299643702075375747072000000 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
See A208650. The trace of a path is a permutation of (1,2,...,n) if and only if the range of the path is {1,2,...,n}.
LINKS
EXAMPLE
Taking n=3:
row 1: {1},{2},{3} ---------> 1,2,3
row 2: {1,2},{1,3},{2,3} ---> 1,1,2,2,3,3
row 3: {1,2,3} -------------> 1,2,3
3 ways to choose a number from row 1,
4 ways to choose a different number from row 2,
1 way to choose remaining number from row 3.
Total: a(3) = 1*4*3 = 12 paths.
MATHEMATICA
p[n_]:=Product[Binomial[n-1, k], {k, 1, n-1}]
Table[p[n], {n, 1, 20}] (* A001142(n-1) *)
Table[p[n]*n, {n, 1, 20}] (* A208650 *)
Table[p[n]*n!, {n, 1, 20}] (* A208651 *)
CROSSREFS
Cf. A208650.
Sequence in context: A367051 A182161 A165950 * A083667 A092124 A009525
KEYWORD
nonn
AUTHOR
Clark Kimberling, Mar 01 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 April 15 10:24 EDT 2024. Contains 371681 sequences. (Running on oeis4.)