A number 
where the 
s
are distinct primes and 
such that
 |
(1)
|
for 
, 2, ..., 
, 
taken as 1, and with 
and 
some fixed integers. For example, 
is a Zeisel
number with 
since
 |
(2)
|
as is 
since
 |
(3)
|
The first few Zeisel numbers are 105, 1419, 1729, 1885, 4505, ... (OEIS A051015), which correspond to constants (1, 2), (4, 
), (1, 6), (2, 3), (3, 2), ....
