STATUS
reviewed
approved
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Revision History for A199660
(Bold, blue-underlined text is an addition; faded, red-underlined text is aShowing entries 1-10 | older changes
Number of parity alternating permutations of [n] avoiding descents from odd to even numbers.
(history; published version)
(history; published version)
STATUS
proposed
reviewed
STATUS
editing
proposed
MATHEMATICA
a[n_] := If[n == 0, 1, With[{r = Quotient[n, 2]},
If[Mod[n, 2] == 0, (2^r+r-1)(r-1)!, r!]]];
Table[a[n], {n, 0, 35}] (* Jean-François Alcover, Oct 30 2021, after Alois P. Heinz *)
STATUS
approved
editing
STATUS
editing
approved
CROSSREFS
Cf. A285672.
STATUS
approved
editing
STATUS
editing
approved
CROSSREFS
Column k=0 of A232187.
STATUS
approved
editing
STATUS
editing
approved
NAME
Number of parity alternating permutations of [n] where an avoiding descents from odd to even element can only have a smaller left neighbor (if any)numbers.
STATUS
approved
editing