A111308 - cp's OEIS frontend

A111308 Sum_{k=1..n} k!! * (n+1-k)!!, where k!! = k(k-2)(k-4)..*(1 or 2).

n	a(n)
0	0
1	1
2	4
3	10
4	28
5	71
6	204
7	556
8	1716
9	5049
10	16884
11	53418
12	193500
13	654639
14	2560140
15	9209016
16	38697300
17	147193425
18	661035060
19	2645445870
20	12627252540
21	52926443415
22	267088884300
23	1167777120420
24	6200158778100
25	28178714373705

[0, 1, 4, 10, 28, 71, 204, 556, 1716, 5049, 16884, 53418, 193500, 654639, 2560140, 9209016, 38697300, 147193425, 661035060, 2645445870, 12627252540, 52926443415, 267088884300, 1167777120420, 6200158778100, 28178714373705]

cp's OEIS Frontend

A111308 Sum_{k=1..n} k!! * (n+1-k)!!, where k!! = k(k-2)(k-4)..*(1 or 2).

Table of values

List of values

cp's OEIS Frontend

A111308 Sum_{k=1..n} k!! * (n+1-k)!!, where k!! = k*(k-2)*(k-4)..*(1 or 2).

Table of values

List of values

A111308 Sum_{k=1..n} k!! * (n+1-k)!!, where k!! = k(k-2)(k-4)..*(1 or 2).