A321855 - cp's OEIS frontend

A321855 Number of permutations f of {1,...,n} such that prime(k)*prime(f(k)) - 2 is prime for every k = 1,...,n.

n	a(n)
1	1
2	1
3	2
4	3
5	5
6	12
7	2
8	3
9	65
10	248
11	448
12	1792
13	4288
14	6468
15	27068
16	29752
17	106066
18	447982
19	1250762
20	6304196
21	46613084
22	126391780
23	504582496
24	2270372946
25	3028652541
26	8941959118
27	36442298864
28	175008626450
29	318369805106
30	1974700703920
31	6654020288821
32	48819526290634
33	150577775767875
34	574885284627624
35	3058310882340228
36	15949743649457780

[1, 1, 2, 3, 5, 12, 2, 3, 65, 248, 448, 1792, 4288, 6468, 27068, 29752, 106066, 447982, 1250762, 6304196, 46613084, 126391780, 504582496, 2270372946, 3028652541, 8941959118, 36442298864, 175008626450, 318369805106, 1974700703920, 6654020288821, 48819526290634, 150577775767875, 574885284627624, 3058310882340228, 15949743649457780]

cp's OEIS Frontend

A321855 Number of permutations f of {1,...,n} such that prime(k)*prime(f(k)) - 2 is prime for every k = 1,...,n.

Table of values

List of values