A212559 - cp's OEIS frontend

A212559 Number of functions f:{1,2,...,n}->{1,2,...,n} such that every non-recurrent element has at most one preimage.

n	a(n)
0	1
1	1
2	4
3	27
4	244
5	2745
6	36966
7	580111
8	10399096
9	209672721
10	4696872490
11	115732052271
12	3110867569140
13	90587751885241
14	2840805169411678
15	95450112571474095
16	3420897993621996016
17	130266500391456691233
18	5252293203395848789842
19	223535386151669737094095
20	10014286301754519472897900

[1, 1, 4, 27, 244, 2745, 36966, 580111, 10399096, 209672721, 4696872490, 115732052271, 3110867569140, 90587751885241, 2840805169411678, 95450112571474095, 3420897993621996016, 130266500391456691233, 5252293203395848789842, 223535386151669737094095, 10014286301754519472897900]

cp's OEIS Frontend

A212559 Number of functions f:{1,2,...,n}->{1,2,...,n} such that every non-recurrent element has at most one preimage.

Table of values

List of values