A068605 - cp's OEIS frontend

A068605 Number of functions from [1,2,...,n] to [1,2,...,n] such that the image contains exactly two elements.

n	a(n)
2	2
3	18
4	84
5	300
6	930
7	2646
8	7112
9	18360
10	45990
11	112530
12	270204
13	638820
14	1490762
15	3440430
16	7864080
17	17825520
18	40107726
19	89652906
20	199229060
21	440401500
22	968883762
23	2122317318
24	4630511064
25	10066329000
26	21810380150
27	47110421826
28	101468601612
29	217969589460
30	467077692570

[2, 18, 84, 300, 930, 2646, 7112, 18360, 45990, 112530, 270204, 638820, 1490762, 3440430, 7864080, 17825520, 40107726, 89652906, 199229060, 440401500, 968883762, 2122317318, 4630511064, 10066329000, 21810380150, 47110421826, 101468601612, 217969589460, 467077692570]

cp's OEIS Frontend

A068605 Number of functions from [1,2,...,n] to [1,2,...,n] such that the image contains exactly two elements.

Table of values

List of values