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A243476 Number of isoscent sequences of length n with exactly three descents. 2

%I

%S 10,216,2765,27214,227847,1708700,11832896,77170252,480381209,

%T 2881934792,16782041642,95373448420,531211249132,2909490548577,

%U 15712454516343,83849134367589,442957532385072,2319975180476948,12061609189508662,62313958408668146,320192732763382270

%N Number of isoscent sequences of length n with exactly three descents.

%H Joerg Arndt and Alois P. Heinz, <a href="/A243476/b243476.txt">Table of n, a(n) for n = 7..100</a>

%t b[n_, i_, t_] := b[n, i, t] = If[n < 1, 1, Expand[Sum[ If[j < i, x, 1] *b[n - 1, j, t + If[j == i, 1, 0]], {j, 0, t + 1}]]] ; a[n_] := Coefficient[b[n - 1, 0, 0], x, 3]; Table[a[n], {n, 7, 40}] (* _Jean-Fran├žois Alcover_, Feb 09 2015, after A242352 *)

%Y Column k=3 of A242352.

%K nonn

%O 7,1

%A _Joerg Arndt_ and _Alois P. Heinz_, Jun 05 2014

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Last modified October 23 22:49 EDT 2019. Contains 328378 sequences. (Running on oeis4.)