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%I #16 May 22 2022 16:39:18
%S 0,1,15,196,2765,44136,803383,16595776,385606089,9980041600,
%T 285072169811,8912986937856,302831517446653,11111352988374016,
%U 437883428985915375,18446566229995503616,827237060699483900177,39346347252746333159424,1978418439209309500803979,104857574454528914145280000
%N a(n) = n^n - (n+1)!/2.
%C This sequence appears as a class of nonsortable words of length n for several unadapted sorting algorithms. For instance this one:
%C - scan all values not at their index position
%C - rotate left 1 step all of them as a cycle
%C - repeat.
%C This is linked to the fact that one can encode the alternating permutations of length n+1 as words of length n.
%t Table[n^n - (n + 1)!/2, {n, 1, 20}]
%Y Cf. A185391 (Complement to n^n of a class of words).
%K nonn,easy
%O 1,3
%A _Olivier GĂ©rard_, Jun 19 2021