A120305 - cp's OEIS frontend

A120305 a(n) = Sum_{i=0..n} Sum_{j=0..n} (-1)^(i+j) * (i+j)!/(i!j!).

n	a(n)
0	1
1	1
2	3
3	9
4	31
5	111
6	407
7	1513
8	5679
9	21471
10	81643
11	311895
12	1196131
13	4602235
14	17757183
15	68680169
16	266200111
17	1033703055
18	4020716123
19	15662273839
20	61092127491
21	238582873475
22	932758045123
23	3650336341239
24	14298633670931

[1, 1, 3, 9, 31, 111, 407, 1513, 5679, 21471, 81643, 311895, 1196131, 4602235, 17757183, 68680169, 266200111, 1033703055, 4020716123, 15662273839, 61092127491, 238582873475, 932758045123, 3650336341239, 14298633670931]

cp's OEIS Frontend

A120305 a(n) = Sum_{i=0..n} Sum_{j=0..n} (-1)^(i+j) * (i+j)!/(i!j!).

Table of values

List of values