OFFSET
1,2
LINKS
Jonathan Beagley and Lara Pudwell, Colorful Tilings and Permutations, Journal of Integer Sequences, Vol. 24 (2021), Article 21.10.4.
FORMULA
a(n) = Sum_{k=2..n+1} k!/2.
a(n) = A054116(n+1)/2.
a(n) = a(n-1) + A001710(n+1).
a(n) ~ n*n!/2. - Stefano Spezia, Jun 29 2021
MATHEMATICA
Accumulate@ Array[#!/2 &, 21, 2] (* Michael De Vlieger, Jun 28 2021 *)
PROG
(PARI) a(n) = sum(k=2, n+1, k!/2); \\ Michel Marcus, Jun 29 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Lara Pudwell, Jun 28 2021
STATUS
approved