OFFSET
1,2
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
Ctibor O. Zizka, May 07 2010
EXTENSIONS
a(4) corrected and more terms from Michel Marcus, Mar 15 2022
STATUS
approved