login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A326253 Number of sequences of distinct ordered pairs of positive integers up to n. 1
1, 2, 65, 986410, 56874039553217, 42163840398198058854693626, 1011182700521015817607065606491025592595137, 1653481537585545171449931620186035466059689728986775126016505970 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..7.

FORMULA

a(n) = A000522(n^2).

EXAMPLE

The a(2) = 65 sequences:

  ()  (11)  (11,12)  (11,12,21)  (11,12,21,22)

      (12)  (11,21)  (11,12,22)  (11,12,22,21)

      (21)  (11,22)  (11,21,12)  (11,21,12,22)

      (22)  (12,11)  (11,21,22)  (11,21,22,12)

            (12,21)  (11,22,12)  (11,22,12,21)

            (12,22)  (11,22,21)  (11,22,21,12)

            (21,11)  (12,11,21)  (12,11,21,22)

            (21,12)  (12,11,22)  (12,11,22,21)

            (21,22)  (12,21,11)  (12,21,11,22)

            (22,11)  (12,21,22)  (12,21,22,11)

            (22,12)  (12,22,11)  (12,22,11,21)

            (22,21)  (12,22,21)  (12,22,21,11)

                     (21,11,12)  (21,11,12,22)

                     (21,11,22)  (21,11,22,12)

                     (21,12,11)  (21,12,11,22)

                     (21,12,22)  (21,12,22,11)

                     (21,22,11)  (21,22,11,12)

                     (21,22,12)  (21,22,12,11)

                     (22,11,12)  (22,11,12,21)

                     (22,11,21)  (22,11,21,12)

                     (22,12,11)  (22,12,11,21)

                     (22,12,21)  (22,12,21,11)

                     (22,21,11)  (22,21,11,12)

                     (22,21,12)  (22,21,12,11)

MATHEMATICA

Table[Sum[k!*Binomial[n^2, k], {k, 0, n^2}], {n, 0, 4}]

CROSSREFS

Cf. A000522, A000595, A002416, A095661, A229865, A326209, A326237, A326251, A326252, A326258.

Sequence in context: A228081 A214366 A220596 * A003821 A055765 A265996

Adjacent sequences:  A326250 A326251 A326252 * A326254 A326255 A326256

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jun 21 2019

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 17 07:39 EDT 2021. Contains 348048 sequences. (Running on oeis4.)