A006040 - cp's OEIS frontend

A006040 a(n) = Sum_{i=0..n} (n!/(n-i)!)^2.

n	a(n)
0	1
1	2
2	9
3	82
4	1313
5	32826
6	1181737
7	57905114
8	3705927297
9	300180111058
10	30018011105801
11	3632179343801922
12	523033825507476769
13	88392716510763573962
14	17324972436109660496553
15	3898118798124673611724426
16	997918412319916444601453057
17	288398421160455852489819933474

[1, 2, 9, 82, 1313, 32826, 1181737, 57905114, 3705927297, 300180111058, 30018011105801, 3632179343801922, 523033825507476769, 88392716510763573962, 17324972436109660496553, 3898118798124673611724426, 997918412319916444601453057, 288398421160455852489819933474]

cp's OEIS Frontend

A006040 a(n) = Sum_{i=0..n} (n!/(n-i)!)^2.

Table of values

List of values