OFFSET
1,4
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..500
FORMULA
a(n) = A008833(n!).
log a(n) ~ n log n. - Charles R Greathouse IV, Apr 04 2012
a(n) = A055772(n)^2. - Amiram Eldar, Jul 26 2024
MAPLE
seq(expand(numtheory[nthpow](n!, 2)), n=1..26); # Peter Luschny, Apr 03 2013
MATHEMATICA
a[n_] := Select[Reverse @ Divisors[n!], IntegerQ[Sqrt[#]] &, 1] // First; a /@ Range[23] (* Jean-François Alcover, May 19 2011 *)
f[p_, e_] := p^(2*Floor[e/2]); a[n_] := Times @@ (f @@@ FactorInteger[n!]); Array[a, 30] (* Amiram Eldar, Jul 26 2024 *)
PROG
(PARI) a(n)=core(n!, 2)[2]^2 \\ Charles R Greathouse IV, Apr 04 2012
(Python)
from math import prod
from itertools import count, islice
from collections import Counter
from sympy import factorint
def A055071_gen(): # generator of terms
c = Counter()
for i in count(1):
c += Counter(factorint(i))
yield prod(p**(e-(e&1)) for p, e in c.items())
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jun 13 2000
EXTENSIONS
More terms from James A. Sellers, Jun 20 2000
STATUS
approved