A307349 - cp's OEIS frontend

A307349 a(n) = Sum_{i=1..n} Sum_{j=1..n} (-1)^(i+j) * (i+j)!/(2!i!j!).

n	a(n)
0	0
1	1
2	1
3	5
4	15
5	56
6	203
7	757
8	2839
9	10736
10	40821
11	155948
12	598065
13	2301118
14	8878591
15	34340085
16	133100055
17	516851528
18	2010358061
19	7831136920
20	30546063745
21	119291436738
22	466379022561
23	1825168170620
24	7149316835465
25	28027993191706
26	109965636641173

[0, 1, 1, 5, 15, 56, 203, 757, 2839, 10736, 40821, 155948, 598065, 2301118, 8878591, 34340085, 133100055, 516851528, 2010358061, 7831136920, 30546063745, 119291436738, 466379022561, 1825168170620, 7149316835465, 28027993191706, 109965636641173]

cp's OEIS Frontend

A307349 a(n) = Sum_{i=1..n} Sum_{j=1..n} (-1)^(i+j) * (i+j)!/(2!i!j!).

Table of values

List of values

cp's OEIS Frontend

A307349 a(n) = Sum_{i=1..n} Sum_{j=1..n} (-1)^(i+j) * (i+j)!/(2!*i!*j!).

Table of values

List of values

A307349 a(n) = Sum_{i=1..n} Sum_{j=1..n} (-1)^(i+j) * (i+j)!/(2!i!j!).