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

10, 216, 2765, 27214, 227847, 1708700, 11832896, 77170252, 480381209, 2881934792, 16782041642, 95373448420, 531211249132, 2909490548577, 15712454516343, 83849134367589, 442957532385072, 2319975180476948, 12061609189508662, 62313958408668146, 320192732763382270

Offset

7,1

Links

Joerg Arndt and Alois P. Heinz, Table of n, a(n) for n = 7..100

Mathematica

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-François Alcover, Feb 09 2015, after A242352 *)

Crossrefs

Column k=3 of A242352.

Sequence in context: A278125 A274763 A002967 * A305107 A294850 A259189

Adjacent sequences: A243473 A243474 A243475 * A243477 A243478 A243479

Keyword

nonn

Author

Joerg Arndt and Alois P. Heinz, Jun 05 2014

Status

approved