A333981 - cp's OEIS frontend

A333981 a(0) = 0; a(n) = 2^(n-1) + (1/n) * Sum_{k=1..n-1} binomial(n,k)^2 * 2^(k-1) * (n-k) * a(n-k).

n	a(n)
0	0
1	1
2	4
3	34
4	576
5	16296
6	691408
7	41069568
8	3252707328
9	331218217600
10	42159307194624
11	6558777387076608
12	1224428872399488000
13	270143735036619436032
14	69534931015726331203584
15	20651854796028308275851264
16	7009822878720340562163007488
17	2696576146784893519040303235072
18	1166999997199470676471689819258880

[0, 1, 4, 34, 576, 16296, 691408, 41069568, 3252707328, 331218217600, 42159307194624, 6558777387076608, 1224428872399488000, 270143735036619436032, 69534931015726331203584, 20651854796028308275851264, 7009822878720340562163007488, 2696576146784893519040303235072, 1166999997199470676471689819258880]

cp's OEIS Frontend

A333981 a(0) = 0; a(n) = 2^(n-1) + (1/n) * Sum_{k=1..n-1} binomial(n,k)^2 * 2^(k-1) * (n-k) * a(n-k).

Table of values

List of values