A375223 - cp's OEIS frontend

A375223 a(n) is the number of permutations of the multiset 1,1, 2,2, ..., n,n such that at least one pair k,k stays at its initial locations 2k-1, 2k.

n	a(n)
1	1
2	1
3	16
4	327
5	11756
6	644315
7	50094570
8	5245258879
9	711662648968
10	121448713262139
11	25460198594647070
12	6431844723440756015
13	1927058631207405670716
14	675631849624828664480107
15	274032655042818911590547266
16	127312224468011793400981895295
17	67167619760422081463964260973200

[1, 1, 16, 327, 11756, 644315, 50094570, 5245258879, 711662648968, 121448713262139, 25460198594647070, 6431844723440756015, 1927058631207405670716, 675631849624828664480107, 274032655042818911590547266, 127312224468011793400981895295, 67167619760422081463964260973200]

cp's OEIS Frontend

A375223 a(n) is the number of permutations of the multiset 1,1, 2,2, ..., n,n such that at least one pair k,k stays at its initial locations 2k-1, 2k.

Table of values

List of values