1. Forum
  2. Usenet
  3. REC.PUZZLES

  • Permutations of (1, 2, ..., N) s.t. No adjacent Numbers are ...

    From henhanna@gmail.com@21:1/5 to All on Sat Nov 5 18:58:20 2022
    i wonder if there's any chance that oeis doesn't mention this.

    1 --> 0
    2 --> 0
    3 --> 0
    4 --> 8 ? (probably more)

    N --> f(N)

    the Number of Permutations of (1, 2, ..., N)
    in which No adjacent Numbers are diff. by 1.



    A good Jumble-generator prob. does this... (== separate original neighbors).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Ilan Mayer@21:1/5 to henh...@gmail.com on Sun Nov 6 07:38:07 2022
    On Saturday, November 5, 2022 at 9:58:21 PM UTC-4, henh...@gmail.com wrote:
    i wonder if there's any chance that oeis doesn't mention this.

    1 --> 0
    2 --> 0
    3 --> 0
    4 --> 8 ? (probably more)

    N --> f(N)

    the Number of Permutations of (1, 2, ..., N)
    in which No adjacent Numbers are diff. by 1.



    A good Jumble-generator prob. does this... (== separate original neighbors).

    https://oeis.org/A002464

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From henhanna@gmail.com@21:1/5 to Ilan Mayer on Sun Nov 6 11:06:30 2022
    On Sunday, November 6, 2022 at 7:38:09 AM UTC-8, Ilan Mayer wrote:
    On Saturday, November 5, 2022 at 9:58:21 PM UTC-4, henh...@gmail.com wrote:
    i wonder if there's any chance that oeis doesn't mention this.

    1 --> 0
    2 --> 0
    3 --> 0
    4 --> 8 ? (probably more)

    N --> f(N)

    the Number of Permutations of (1, 2, ..., N)
    in which No adjacent Numbers are diff. by 1.



    A good Jumble-generator prob. does this... (== separate original neighbors).


    https://oeis.org/A002464


    thansk!


    Hertzsprung's problem: ways to arrange n non-attacking kings on an n X n board, with 1 in each row and column. Also number of permutations of length n without rising or falling successions.
    (Formerly M2070 N0818)
    1, 1, 0, 0, 2, 14, 90, 646, 5242, 47622, 479306, 5296790, 63779034, 831283558, 11661506218,


    How did they get 2 ?

    2413, (and its reverse) ------- omg.. that is 2


    # _ # _
    _ _ _ _
    _ # _ #
    _ _ _ _


    # _ # _
    _ _ _ _
    # _ # _
    _ _ _ _


    # _ # _
    _ _ _ _
    _ _ _ _
    # _ # _


    # _ # _
    _ _ _ _
    _ _ _ _
    _ # _ #


    # _ # _
    _ _ _ _
    _ _ _ #
    # _ _ _

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)