|
|
A175411
|
|
a(n) = Sum_{i=(n*n-n+2)/2..(n*n+n)/2} i!.
|
|
0
|
|
|
1, 8, 864, 4037040, 1401598598400, 53652268264218624000, 316196664157721349185863680000, 382630662500715988102392981826830336000000, 122342346998826334909002798912467017444232685158400000000, 12931604174610554670466196146308122246477496321113350463375278080000000000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
EXAMPLE
|
a(4) = 7! + 8! + 9! + 10! = 4037074.
|
|
PROG
|
(PARI) a(n)= sum(i=(n^2-n+2)/2, (n^2+n)/2, i!); \\ Michel Marcus, Mar 15 2022
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|