A026124 - cp's OEIS frontend

A026124 a(n) = number of (s(0),s(1),...,s(n)) such that every s(i) is a nonnegative integer, s(0) = 1, s(n) = 3, |s(1) - s(0)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2. Also a(n) = T(n,n-2), where T is the array in A026120.

n	a(n)
2	1
3	2
4	7
5	20
6	59
7	170
8	489
9	1400
10	4002
11	11428
12	32626
13	93160
14	266136
15	760800
16	2176644
17	6232896
18	17864841
19	51253794
20	147188535
21	423098404
22	1217371023
23	3505992050
24	10106384621
25	29158627592
26	84200265555
27	243345531806
28	703858089717

[1, 2, 7, 20, 59, 170, 489, 1400, 4002, 11428, 32626, 93160, 266136, 760800, 2176644, 6232896, 17864841, 51253794, 147188535, 423098404, 1217371023, 3505992050, 10106384621, 29158627592, 84200265555, 243345531806, 703858089717]

cp's OEIS Frontend

A026124 a(n) = number of (s(0),s(1),...,s(n)) such that every s(i) is a nonnegative integer, s(0) = 1, s(n) = 3, |s(1) - s(0)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2. Also a(n) = T(n,n-2), where T is the array in A026120.

Table of values

List of values