A001253 Number of permutations of order n with the length of longest run equal to 5. (Formerly M2123 N0840)

0, 0, 0, 0, 2, 20, 198, 2048, 22468, 264538, 3340962, 45173518, 652209564, 10024669626, 163546399460, 2823941647390, 51468705947590, 987671243816650, 19909066390361346, 420650676776338140, 9297308938203169622, 214562999510569012168

Offset

1,5

References

F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 262. (Terms for n>=13 are incorrect.)

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Alois P. Heinz, Table of n, a(n) for n = 1..450 (first 100 terms from Max Alekseyev)

Max A. Alekseyev, On the number of permutations with bounded runs length, arXiv preprint arXiv:1205.4581 [math.CO], 2012-2013. - From N. J. A. Sloane, Oct 23 2012

Mathematica

length = 5;
g[u_, o_, t_] := g[u, o, t] = If[u+o == 0, 1, Sum[g[o + j - 1, u - j, 2], {j, 1, u}] + If[t<length, Sum[g[u + j - 1, o - j, t+1], {j, 1, o}], 0]];
b[u_, o_, t_] := b[u, o, t] = If[t == length, g[u, o, t], Sum[b[o + j - 1, u - j, 2], {j, 1, u}] + Sum[b[u + j - 1, o - j, t + 1], {j, 1, o}]];
a[n_] := Sum[b[j - 1, n - j, 1], {j, 1, n}];
Table[a[n], {n, 1, 30}] (* Jean-François Alcover, Aug 18 2018, after Alois P. Heinz *)

Crossrefs

Cf. A001250, A001251, A001252, A010026, A211318.

Sequence in context: A348886 A001078 A299865 * A303462 A085586 A322298

Adjacent sequences: A001250 A001251 A001252 * A001254 A001255 A001256

Keyword

nonn

Author

N. J. A. Sloane

Extensions

Corrected and extended by Max Alekseyev at the suggestion of Sean A. Irvine, May 04 2012

Status

approved