A138770 - cp's OEIS frontend

A138770 Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} such that there are exactly k entries between the entries 1 and 2 (n>=2, 0<=k<=n-2).

n	a(n)
2	2
3	4
4	2
5	12
6	8
7	4
8	48
9	36
10	24
11	12
12	240
13	192
14	144
15	96
16	48
17	1440
18	1200
19	960
20	720
21	480
22	240
23	10080
24	8640
25	7200
26	5760
27	4320
28	2880
29	1440
30	80640
31	70560
32	60480
33	50400
34	40320
35	30240
36	20160
37	10080
38	725760
39	645120
40	564480
41	483840
42	403200
43	322560
44	241920
45	161280
46	80640

[2, 4, 2, 12, 8, 4, 48, 36, 24, 12, 240, 192, 144, 96, 48, 1440, 1200, 960, 720, 480, 240, 10080, 8640, 7200, 5760, 4320, 2880, 1440, 80640, 70560, 60480, 50400, 40320, 30240, 20160, 10080, 725760, 645120, 564480, 483840, 403200, 322560, 241920, 161280, 80640]

cp's OEIS Frontend

A138770 Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} such that there are exactly k entries between the entries 1 and 2 (n>=2, 0<=k<=n-2).

Table of values

List of values