A026270 - cp's OEIS frontend

A026270 Number of (s(0), s(1), ..., s(n)) such that every s(i) is a nonnegative integer, s(0) = 0, s(1) = 1 = s(n), |s(i) - s(i-1)| <= 1 for i >= 2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also T(n,n-1), where T is the array in A026268.

n	a(n)
2	1
3	2
4	6
5	15
6	39
7	102
8	270
9	721
10	1941
11	5262
12	14354
13	39372
14	108528
15	300482
16	835278
17	2330334
18	6522882
19	18313542
20	51559506
21	145530291
22	411738723
23	1167450066
24	3316925794
25	9441771081
26	26923831029
27	76901809810
28	219992462862
29	630245628681
30	1808029517585

[1, 2, 6, 15, 39, 102, 270, 721, 1941, 5262, 14354, 39372, 108528, 300482, 835278, 2330334, 6522882, 18313542, 51559506, 145530291, 411738723, 1167450066, 3316925794, 9441771081, 26923831029, 76901809810, 219992462862, 630245628681, 1808029517585]

cp's OEIS Frontend

A026270 Number of (s(0), s(1), ..., s(n)) such that every s(i) is a nonnegative integer, s(0) = 0, s(1) = 1 = s(n), |s(i) - s(i-1)| <= 1 for i >= 2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also T(n,n-1), where T is the array in A026268.

Table of values

List of values