A026123 - cp's OEIS frontend

A026123 a(n) = number of (s(0),s(1),...,s(n)) such that every s(i) is a nonnegative integer, s(0) = 1, s(n) = 2, |s(1) - s(0)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2. Also a(n) = T(n,n-1), where T is the array in A026120; a(n) = U(n,n+1), where U is the array in A026148.

n	a(n)
2	1
3	4
4	10
5	28
6	76
7	209
8	575
9	1589
10	4405
11	12253
12	34189
13	95679
14	268503
15	755457
16	2130717
17	6023235
18	17063139
19	48434514
20	137741280
21	392407134
22	1119766942
23	3200326627
24	9160055809
25	26254474379
26	75348899051
27	216515177336
28	622887159274

[1, 4, 10, 28, 76, 209, 575, 1589, 4405, 12253, 34189, 95679, 268503, 755457, 2130717, 6023235, 17063139, 48434514, 137741280, 392407134, 1119766942, 3200326627, 9160055809, 26254474379, 75348899051, 216515177336, 622887159274]

cp's OEIS Frontend

A026123 a(n) = number of (s(0),s(1),...,s(n)) such that every s(i) is a nonnegative integer, s(0) = 1, s(n) = 2, |s(1) - s(0)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2. Also a(n) = T(n,n-1), where T is the array in A026120; a(n) = U(n,n+1), where U is the array in A026148.

Table of values

List of values