OFFSET
0,4
EXAMPLE
a(3) = 4 because (3!)! = 6! = 720 = 1011010000_2 which has 4 ones.
MAPLE
a:= n-> add(i, i=Bits[Split](n!!)):
seq(a(n), n=0..10);
MATHEMATICA
a[n_] := DigitCount[(n!)!, 2, 1]; Array[a, 10, 0] (* Amiram Eldar, Oct 29 2021 *)
PROG
(Python)
from gmpy2 import fac, popcount
def A348651(n): return popcount(fac(fac(n))) # Chai Wah Wu, Oct 28 2021
(PARI) a(n) = hammingweight((n!)!); \\ Michel Marcus, Oct 29 2021
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Alois P. Heinz, Oct 27 2021
EXTENSIONS
a(11)-a(12) from Chai Wah Wu, Oct 28 2021
STATUS
approved