A162976 - cp's OEIS frontend

A162976 Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k double descents and initial descents (n>=0; 0<=k<=max(0,n-1)) [we say that i is a doubledescent of a permutation p if p(i) > p(i+1) > p(i+2); we say that a permutation p has an initial descent if p(1) > p(2)].

n	a(n)
0	1
1	1
2	1
3	1
4	3
5	2
6	1
7	9
8	11
9	3
10	1
11	39
12	48
13	28
14	4
15	1
16	189
17	297
18	166
19	62
20	5
21	1
22	1107
23	1902
24	1419
25	476
26	129
27	6
28	1
29	7281
30	14391
31	11637
32	5507
33	1235
34	261
35	7
36	1
37	54351
38	118044
39	111438
40	56400
41	19096
42	3020
43	522
44	8
45	1
46	448821
47	1078245
48	1119312
49	673128
50	239146
51	61986

[1, 1, 1, 1, 3, 2, 1, 9, 11, 3, 1, 39, 48, 28, 4, 1, 189, 297, 166, 62, 5, 1, 1107, 1902, 1419, 476, 129, 6, 1, 7281, 14391, 11637, 5507, 1235, 261, 7, 1, 54351, 118044, 111438, 56400, 19096, 3020, 522, 8, 1, 448821, 1078245, 1119312, 673128, 239146, 61986]

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