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A345461 Triangle T(n,k) (n >= 1, 0 <= k <= n-1) read by rows: number of distinct permutations after k steps of the "optimist" algorithm.

%I A345461 #24 Aug 11 2021 09:17:52
%S A345461 1,2,1,6,1,1,24,6,1,1,120,38,7,1,1,720,232,53,7,1,1,5040,1607,404,74,
%T A345461 7,1,1,40320,12984,3383,732,108,7,1,1,362880,117513,31572,7043,1292,
%U A345461 167,9,1,1,3628800,1182540,324112,75350,14522,2384,260,11,1,1
%N A345461 Triangle T(n,k) (n >= 1, 0 <= k <= n-1) read by rows: number of distinct permutations after k steps of the "optimist" algorithm.
%C A345461 Start with the n! permutations of order n. Apply an iteration of the "optimist" sorting algorithm. Count the distinct permutations, until all are sorted.
%C A345461 The length of each row is n.
%C A345461 The optimist algorithm is: rotate right all currently unsorted letters by the distance between the first unsorted one and its sorted position. An example is given in A345453.
%F A345461 T(n,0) = n!; T(n,n-1) = 1; T(n,n-2) = 1 for n > 2.
%e A345461 Triangle begins:
%e A345461 .
%e A345461      1;
%e A345461      2,     1;
%e A345461      6,     1,    1;
%e A345461     24,     6,    1,   1;
%e A345461    120,    38,    7,   1,  1;
%e A345461    720,   232,   53,   7,  1,  1;
%e A345461   5040,  1607,  404,  74,  7,  1,  1;
%e A345461 .
%Y A345461 Cf. A345453 (permutations according to number of steps for sorting).
%Y A345461 Cf. A321352 and A008305 (the equivalent for Eulerian numbers).
%Y A345461 Cf. A345462 (the equivalent for Stirling numbers of 1st kind).
%Y A345461 Cf. A345464 (first column).
%K A345461 tabl,nonn
%O A345461 1,2
%A A345461 _Olivier Gérard_, Jun 20 2021