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A230132 Number of permutations of order n with the length of longest run equal 9. 3

%I

%S 2,36,574,9024,145080,2419872,42129360,767370240,14631376500,

%T 291914163322,6088804487138,132624737931726,3012939864521998,

%U 71296697740927172,1755099895042102380,44889002698811118240,1191389820174200208622,32774409073391657243622

%N Number of permutations of order n with the length of longest run equal 9.

%H Alois P. Heinz, <a href="/A230132/b230132.txt">Table of n, a(n) for n = 9..450</a>

%p g:= proc(u, o, t) option remember; `if`(u+o=0, 1,

%p add(g(o+j-1, u-j, 2), j=1..u) +`if`(t<9,

%p add(g(u+j-1, o-j, t+1), j=1..o), 0))

%p end:

%p b:= proc(u, o, t) option remember; `if`(t=9, g(u, o, t),

%p add(b(o+j-1, u-j, 2), j=1..u)+

%p add(b(u+j-1, o-j, t+1), j=1..o))

%p end:

%p a:= n-> add(b(j-1, n-j, 1), j=1..n):

%p seq(a(n), n=9..30);

%t length = 9;

%t 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]];

%t 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}]];

%t a[n_] := Sum[b[j - 1, n - j, 1], {j, 1, n}];

%t Table[a[n], {n, length, 30}] (* _Jean-Fran├žois Alcover_, Aug 18 2018, after _Alois P. Heinz_ *)

%Y Column l=9 of A211318.

%Y A diagonal of A010026.

%K nonn

%O 9,1

%A _Alois P. Heinz_, Oct 10 2013

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Last modified September 19 08:05 EDT 2021. Contains 347556 sequences. (Running on oeis4.)