A227918 - cp's OEIS frontend

A227918 Sum over all permutations beginning and ending with ascents, and without double ascents on n elements and each permutation contributes 2 to the power of the number of double descents.

n	a(n)
2	1
3	0
4	5
5	22
6	137
7	956
8	7653
9	68874
10	688745
11	7576192
12	90914309
13	1181886014
14	16546404201
15	248196063012
16	3971137008197
17	67509329139346
18	1215167924508233
19	23088190565656424
20	461763811313128485
21	9697040037575698182
22	213334880826665360009
23	4906702259013303280204
24	117760854216319278724901

[1, 0, 5, 22, 137, 956, 7653, 68874, 688745, 7576192, 90914309, 1181886014, 16546404201, 248196063012, 3971137008197, 67509329139346, 1215167924508233, 23088190565656424, 461763811313128485, 9697040037575698182, 213334880826665360009, 4906702259013303280204, 117760854216319278724901]

cp's OEIS Frontend

A227918 Sum over all permutations beginning and ending with ascents, and without double ascents on n elements and each permutation contributes 2 to the power of the number of double descents.

Table of values

List of values