The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A242154 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A242154

Number of ascent sequences of length n with exactly one flat step.
(history; published version)

#10 by Bruno Berselli at Tue Feb 10 05:59:59 EST 2015

STATUS

proposed

approved

#9 by Jean-François Alcover at Tue Feb 10 05:14:26 EST 2015

STATUS

editing

proposed

#8 by Jean-François Alcover at Tue Feb 10 05:14:20 EST 2015

MATHEMATICA

b[n_, i_, t_] := b[n, i, t] = If[n == 0, 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, -1], x, 1]; Table[ a[n], {n, 2, 30}] (* Jean-François Alcover, Feb 10 2015, after A242153 *)

STATUS

approved

editing

#7 by Vaclav Kotesovec at Wed Aug 27 18:14:08 EDT 2014

STATUS

editing

approved

#6 by Vaclav Kotesovec at Wed Aug 27 18:14:02 EDT 2014

FORMULA

a(n) ~ 2*sqrt(3)/(exp(Pi^2/12)*sqrt(Pi)) * (6/Pi^2)^n * n! * sqrt(n). - Vaclav Kotesovec, Aug 27 2014

STATUS

approved

editing

#5 by Alois P. Heinz at Mon May 05 19:27:52 EDT 2014

STATUS

editing

approved

#4 by Alois P. Heinz at Mon May 05 19:25:05 EDT 2014

LINKS

Joerg Arndt and Alois P. Heinz, <a href="/A242154/b242154.txt">Table of n, a(n) for n = 2..140</a>

#3 by Alois P. Heinz at Mon May 05 15:34:43 EDT 2014

AUTHOR

_Joerg Arndt_ and _Alois P. Heinz_, May 05 2014

#2 by Alois P. Heinz at Mon May 05 15:33:37 EDT 2014

NAME

allocated for Alois P. Heinz

Number of ascent sequences of length n with exactly one flat step.

DATA

1, 2, 6, 20, 80, 366, 1897, 10976, 70155, 490930, 3733246, 30655152, 270334766, 2548153230, 25566585450, 272052199520, 3060191748695, 36282298766760, 452220051658265, 5911274512571280, 80862988937379390, 1155309461910323610, 17208404375488550100

OFFSET

2,2

CROSSREFS

Column k=1 of A242153.

KEYWORD

allocated

nonn

AUTHOR

Alois P. Heinz, May 05 2014

STATUS

approved

editing

#1 by Alois P. Heinz at Mon May 05 12:03:39 EDT 2014

NAME

allocated for Alois P. Heinz

KEYWORD

allocated

STATUS

approved