OFFSET
1,2
COMMENTS
Least k > 0 such that k^n/A002805(n) is an integer.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..2370
EXAMPLE
For n = 6, the denominator of Sum_{i=1..6} 1/i is 20 = 2^2*5, so a(7) = 2*5 = 10.
PROG
(PARI) a(n) = factorback(factorint(denominator(sum(i=2, n, 1/i)))[, 1]);
(Python)
from functools import reduce
from operator import mul
from sympy import harmonic, factorint
def A333196(n):
fs = factorint(harmonic(n).q)
return 1 if len(fs) == 0 else reduce(mul, (p**(fs[p]//n + 1 if fs[p] % n else fs[p]//n) for p in fs)) # Chai Wah Wu, Apr 03 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Jinyuan Wang, Mar 10 2020
STATUS
approved