A120279 - cp's OEIS frontend

A120279 a(n) = Sum[Sum[(i+j)!/i!/j!,{i,1,j}],{j,1,n}].

n	a(n)
1	2
2	11
3	45
4	170
5	631
6	2346
7	8780
8	33089
9	125466
10	478181
11	1830258
12	7030557
13	27088856
14	104647615
15	405187809
16	1571990918
17	6109558567
18	23782190466
19	92705454875
20	361834392094
21	1413883873953
22	5530599237752
23	21654401079301
24	84859704298176

[2, 11, 45, 170, 631, 2346, 8780, 33089, 125466, 478181, 1830258, 7030557, 27088856, 104647615, 405187809, 1571990918, 6109558567, 23782190466, 92705454875, 361834392094, 1413883873953, 5530599237752, 21654401079301, 84859704298176]

cp's OEIS Frontend

A120279 a(n) = Sum[Sum[(i+j)!/i!/j!,{i,1,j}],{j,1,n}].

Table of values

List of values